Welcome to Criminal Justice Access

Greetings everyone,

For November at criminaljusticeaccess.com, be sure to check out Research Briefs and explore an improved understanding of jurors’ assessment of eyewitness testimony, learn about profiling efforts to distinguish between single victim and serial rapists, understand how marijuana using mental health professionals relate risk to their marijuana using clients, and consider crime incident risk factors that support the use of tactical officers as opposed to their reported over-use.

Research Briefs

Evaluating Witness Testimony: Juror Knowledge, False Memory, and the Utility of Evidence-Based Directions

Helm, The International Journal if Evidence & Proof, 2021

Helm states that there is a general assumption that jurors are capable of accurately assessing the truthfulness of witnesses, including the accuracy of their recollections of the incident in question, based on their own experiences with memory recall. However, research in law and the cognitive sciences suggest that they do in fact have difficulty assessing the validity of other individuals’ memories. Jurors understand that factors like fearful and stressful emotions and intoxication,  and observation circumstances such as distance from an event or lighting, will affect the recording of a memory. However they are less knowledgeable about the factors that affect memory recall, such as suggestion, after the memory is encoded, which can alter the recall of specifics or generate inaccurate or nonexistent events. This is problematic as false or misleading eyewitness testimony has been identified as a leading cause of wrongful convictions. Distinguishing between true and false memories can be challenging and jurors likely have a poor understanding of the cues that suggest a memory could be false. Juries are provided little guidance in identifying false memories and make mistakes based on intuitive concepts of memories rather than established cognitive science. Helm suggests  how legal procedure can facilitate the presentation of information in this way, specifically in cases involving potential false memory.

False memories can be generated in a few ways. For example, source misattribution can occur when people are incapable of distinguishing between two or more sources of their memories. The image that people generate in their minds when thinking about an occurrence can be confused and misattributed to something that happened in reality. False memories can also be generated spontaneously when people recall the gist of something occurring. This familiarity with a  person or event but not a specific, verbatim, precise recollection can result in a false memory For example, recalling a general description of an offender may produce a familiarity but is lacking in enough precise details that would determine the suspect is not a true match for the offender, which results in misidentification of a suspect. Helm also notes that “spontaneous false memory can also arise as a result of what is known as change blindness where a witness does not notice that a perpetrator and a bystander are actually different people. These errors can lead to an occurrence known as unconscious transference, or the familiar bystander effect. This effect refers to a memory error whereby a witness identifies a familiar, but innocent person, as an offender. For example, research has shown a tendency to misidentify an innocent bystander to a crime as an offender or to identify a familiar person from an entirely different context as an offender”.

While research has demonstrated how false memories can occur and is well accepted and understood in legal contexts, lay persons’ viewpoints on the generation of false memories diverge from the experts and as well are over confidant in the accuracy of memories. Helm states this lack of  understanding must be accounted for and corrected by legal procedure. Direction can be provided to jurors, warning them of a need for caution before convicting a defendant in reliance on the correctness of the identification, debunk relevant memory “myths” (such as the belief that a confident witness is always reliable), list potential influential encoding factors, or explain relevant discrepancies in witness statements. It is also possible to call expert witnesses to explain memory pitfalls to jurors and judges.

Helm states that “in order to be effective, directions relating to witness memory must both appropriately alter juror knowledge relating to witness memory, and facilitate the application of that knowledge in a case context.” However in referencing the Turnbull directions in use in England and Wales, they may do neither  and are essentially ineffective. As in the U.S., judges are not memory experts and the application of juror direction is dependent on the discretion of judges and that many cases are moved through the system based solely on eyewitness information. However, even if accurate information regarding memory is presented to jurors there may be a problem in the delivery of this information through a relatively superficial judicial direction following the presentation of the evidence. With jurors having their own “common sense” intuitions of about memory that needs to be dispelled, the relevant research and information about memory must be related with enough detail and background to  be persuasive enough to update jurors beliefs. To influence jurors a more central direct approach may not be influential enough to change jurors’ minds.  For example simply giving direction to the jurors that a confidant witness may not be accurate will be unlikely to change a juror’s mind as it lacks the meaningful information for the jurors to evaluate and substantiate the claim.

A different approach to jurors may be necessary as research indicates the leading model of jury decision making, the Story Model, indicates juries make decision by a narrative “story” organization on trial information. Evidence is incorporated into a narrative that explains what happened and verdicts are reached by matching the best fitting narrative to a verdict category. Their mental representations of evidence in story structure indicate that “jurors are more likely to remember evidence that is consistent with the story associated with their verdict, and that jurors are likely to find evidence more important where that evidence has a causal role in the story that is associated with their verdict”. Existing direction on witness testimony based on their recollections is insufficient to establish an understanding with jurors how those concerns may apply or how they fit into their narratives. For example, not being given detailed information, based on research, on the types of situations were witnesses may not be reliable or credible, or how jurors can be helped evaluate whether the “confident witness” is indeed accurate. Also, directions may be too cursory to be effectively incorporated into their narratives. Jurors too often consider the overall gist, or inferred meaning  of the evidence,  provided rather than verbatim details. It’s thus necessary to make the evidence and directions regarding it more meaningful to jurors, which will facilitate more informed decision making. Overly simplified directions by a judge that “warns the jury that even a witness who is very confident may be incorrect, but without being told why this might be the case, or being given examples of the types of other cases in which memory has been impaired in this way, it is likely to be difficult for jurors to extract meaning from it appropriately”. Lacking this context may result in either jurors being dismissive of all witness evidence, jurors not attributing meaning to the information at all and disregarding it in  decision making, or  attributing meaning to the information in a biased way-judging the importance of the warning based on their unrelated conceptions of the case-for example if they feel overall that the defendant seems guilty they might conclude that although confident witnesses can be wrong, the confidence in the case at hand does signal accuracy. A third problem exists if the directions are not provided prior to the presentation of evidence as it will be difficult for jurors to incorporate this new information into a narrative that has already been constructed or they will simply alter the understanding of this new information to fit into the already established narrative.

Helm states to be effective juror instruction about the accuracy and validity of witness testimony should follow these guidelines:

  • Provide jurors with sufficient information to allow them to evaluate the case for the conclusions presented and update their beliefs accordingly.
  • Provide jurors with sufficient information to allow them to understand the types of cases in which particular concerns may be important, and why; and
  • Instructions that are consistently given prior to the presentation of case evidence in order to inform juror narrative construction from evidence, and to reduce effects of motivated cognition or confirmatory bias in juror interpretation and analysis of information given.

Helm’s recent research sought support for these contentions utilizing 411  participants as mock jurors reading case vignettes. Participants were grouped into no instruction, basic instruction, and detailed training instruction groups and were also asked a series of memory questions rating their agreement with statements regarding 1) Eyewitness testimony about an event often reflects not only what they actually saw but also information they obtained later on, 2) Eyewitnesses sometimes identify as a culprit someone they have seen in another situation or context, and 3) An eyewitness’s confidence can be influenced by factors that are unrelated to identification accuracy. Helm’s results provide support for more in-depth training instruction for jurors. Basic instruction did increase consensus with existing scientific research on false memory compared to no instruction to a small degree. However, the training instruction was clearly more effective at increasing the level of juror belief with the scientific consensus. The training group, but not the basic instruction group, also indicated an influence on case outcomes. In vignettes with weak evidence less guilty verdicts were produced, however in strong evidence cases the training direction did not influence the number of guilty verdicts, which Helm states demonstrated that training directions helped jurors effectively identify an enhanced risk of false memory, rather than just introducing a general skepticism of towards any eyewitness testimony.

While the study did have some limitations it did indicate that more specific detailed instruction can assist jurors in making informed decisions and can be utilized with other juror misconceptions such as witnesses that are inconsistent are lying or mistaken (when they could be influenced by trauma), or in using them to dispel rape myths. Helm states more work needs to be done in research with real life juries, which can lead to policy that can be put into actual practice in the courtroom.

Helm, R. K. (2021). Evaluating witness testimony: Juror knowledge, false memory, and the utility of evidence-based directions. The International Journal of Evidence & Proof, 25(4), 264-285.

Predicting Rapist Type Based on Crime-Scene Violence, Interpersonal Involvement, and Criminal Sophistication in U.S. Stranger Rape Cases

Mellick, Jeglic, Bogaard, International Journal of Police Science & Management, 2021

The authors contend that in stranger rape cases, physical evidence like DNA and fingerprints may be absent or inconclusive and that in these cases, offender profiling, linking crime scene behavior to an offender, may be useful in resolving those cases. Similarities in crime scene behaviors may point to offenders whose past offenses may have exhibited the same behaviors or suggest a certain type of offender has perpetrated the offenses.

While offender profiling may in some ways be lacking scientific rigor, two assumptions underlie profiling: the consistency assumption and the homology assumption. Consistency assumes that the actions of any offender are consistent across offenses, i.e. there will be a repetition of particular aspects of behavior if the same offender engages in the same type of offense again, such as in serial murder or serial rape. Homology assumes a likeness between the character of an offender and the behavior they engage in at a crime scene, so rather than differentiating between offenders by the presence or absence of singular individual behaviors  it examines groups of behaviors across groups of offenders. This “accounts for the possibility that a serial offender may not engage in the exact same behavior across a series of crimes, or likewise, that two different offenders may not engage in the same exact behavior but have rather thematically similar behavior”.

Rapists can be classified based on their behavioral themes by analyzing their crime scene behavior. As these offenders interact with other people in a similar way in non-criminal scenarios, they will interact with victims in a similar way during their offenses. This means it’s possible to link a crime and offender based on their behavioral themes. So a serial offender will exhibit similar behavior across similar offenses, and offender distinctiveness, meaning that two offenders will not behave in the exact same way, makes it possible to distinguish between them.

The authors state that previous research has found different themes explain the differences between rapists; themes of hostility, involvement, and control. Hostility entails overtly aggressive interaction, involvement pertains to physical or verbal attempted contact with the victim such as kissing, complimenting, or reassuring the victim, and control utilizes a surprise attack or weapon to control the victim. Other research suggests similar theme methodology, such as hostility, dominance, and compliance gaining. However, the behaviors tied to these themes may be altered or varied in the offense depending on the context of the situation, namely the victims behavior, making analysis of the factors important in understanding offender behavior. Offenders’ level of initiating violence, victim age, and offender mobility are all factors that will affect the characteristics of the behavioral themes, Offenders will also decide how to act based on the effort, rewards, and costs involved in their course of action which contributes to their profile.

The authors state it’s also important to distinguish between single victim rapists and serial rapists but there has been little research examining the differences between the two. However, research has indicated that single victim rapists are usually known to their victims and use a confidant approach compared to the overwhelming characteristics of serial rapists being strangers to their victims and utilizing surprise attacks. Some research in this area indicates more violence and interpersonal contact (such as inducing the victim to participate) with single victim rapists than serial rapists, however serial rapists show more criminal sophistication (in avoidance of detection and apprehension) in comparison. While stranger rape is more difficult for the police to investigate, their crime scene characteristics can be used to profile offenders. The authors contend that while research has examined serial rapes, single victim rapes, and stranger rapes separately, or comparing serial rapists to single victim rapists, no studies have compared single victim rapes and serial rapes in the stranger rapist context. In the authors’ study, they sought to examine these differences in the stranger rape context  hypothesizing that single victim rapists would use more violence and interpersonal contact while serial rapists would show a greater criminal sophistication than there single victim counterparts.

Utilizing the case files of 3,168 male sex offenders they composed a sub-sample of stranger rapes involving 244 single victim rapists (SVR) and 141 serial rapists (SER) (37% White, 47% Black, and 14% Latino) whose victims were 84% female. The violence component examined the amount of physical violence and included offender threats and oral, anal, and digital penetration. The criminal sophistication component involved, the use of weapons, drugs and alcohol, isolation of the offense location, bondage or incapacitation of the victim, and grooming or luring the victim. The interpersonal theme examined whether the offender caressed the victim, performed oral sex on them, induced participation, or introduced pornography into the crime.

Significant differences were found in the demographics of SVR and SER with most SVR being single while SER tended to be divorced. Significant racial differences were also found. While SVR were more evenly represented  among White (35%), Black (45%) and Latino (18%), the SER sub-sample demonstrated fewer Latinos were represented (8%) and Whites comprised 40% and Blacks 51%.

Significant differences existed in the three crime scene behaviors between SVR and SER. In the violence theme there were no significant differences between most penetration and actual physical violence between the two groups however, SVR were more likely to use threats of violence and digital penetration compared to SER. Significant differences were also found in different areas of criminal sophistication. Compared to SVR, SER were significantly more likely to use a weapon, more likely  to use a gun or knife as a weapon, incapacitate/choke their victims, and groom/meet or lure their victims to a location. However SVR were more likely to have used drugs or alcohol during the crime and commit the crime in an unknown or new location, compared to SER. The only significant difference in the interaction theme was that SER were more likely to induce participation from the victims compared to SVR. The significant characteristics, placed in a logistic regression model for prediction of type of rapist was found to explain 35% of the variance in rapist type and overall correctly classified 75.8 percent of the type of rapist cases.

The authors conclude that  “these findings could be used to identify potential suspects in stranger rape cases because the crime scene information could help law enforcement determine whether they are looking for individuals who have committed these types of crimes previously and may already be in the system”. They also suggest that “the crime-scene behaviors associated with serial rapists could also be used to identify unknown offenders as possible serial offenders. This includes individuals who may have committed sexual offenses before, but who have never been caught and cases where offenders have just started their rape career. This allows for law enforcement to narrow down their suspect pool and thus assist the investigation”.

While this study is exploratory the findings can guide future research by testing the predictive power in actual crime scenes as well as more closely examine different regions and cultural groups as well as include more crime scene characteristics not examined here such as developmental factors, triggering behaviors before an attack, or the cognitive processes involved in the offender’s planning before an attack.

Mellink, I. S., Jeglic, E. L., & Bogaard, G. (2021). Predicting rapist type based on crime-scene violence, interpersonal involvement, and criminal sophistication in US stranger rape cases. International Journal of Police Science & Management, 14613557211036564.

Cannabis Use Among Mental Health Professionals: A Qualitative Study of Cannabis-Related Risk Perceptions

Ghelani, Journal of Drug Issues, 2021

The author recognizes that there are potential risks and harms in marijuana use. Research indicates the potential for issues of dependence, cognitive deficits, anxiety, and the risks of driving while intoxicated. These risks may be poorly understood or not attributed to marijuana use if users assume that marijuana is considered to be harmless, specifically considering the current legal status of marijuana in Canada.. The author explores whether mental health professionals who were themselves marijuana users, were cognizant of the risks that do exist in treating individuals who were also marijuana users.

The small qualitative Canadian study consisted of seven professionals (three social workers, two psychotherapists, a nurse, and a nurse practitioner) whose clients worked with marijuana users and explored the extent that study participants were aware of and addressed marijuana use risk with their clients and in their own use.

Overall, all the participants recognized the psychosocial risks involved in marijuana use by their clients and in some cases, when relevant, in their own use. Anxiety, panic, and avoidance behavior was the most prevalent risks mentioned by the participants, especially amongst young and/or inexperienced users, though two participants noted they do experience some anxiety in social situations. Most of the participants noted that marijuana use could also negatively affect interpersonal relationships through anxiety caused by peer pressure or a fear of separation from their peers who used. Some participants noted the effects on clients stemming from tension in parental or spousal relationships from non-users, as well as the social stigma that results when their clients are viewed as “criminal”, a “stoner”, or ” lazy” because of their marijuana use. The participants were also very well aware of the dangers of driving while intoxicated on marijuana and related how chronic use may also affect employment if their clients’ jobs require the operation of a vehicle.

Beyond social issues, the participants also discussed the cognitive and neurological impairments and risks their clients might face or experience. Five of the participants discussed how marijuana use could lead to psychosis and exacerbate symptoms of schizophrenia. The suggestion put forth to their clients was to stop using cannabis because they were experiencing symptoms along  the schizophrenic spectrum, with some participants noting that cannabis has the potential to make young people more vulnerable to psychosis or for long term users to  be more resistant to anti-psychotic medications. Most of participants discussed how cognitive functioning could be impaired, especially in the brains of adolescents and young adults, cautioning against their use of marijuana. Some participants discussed the possibility of decreased motivation and reduced day to day function with some clients as well as how it may affect memory, attention, and concentration. Two participants themselves noted that it decreases their concentration and smoking too much “allows their mind to wander”. Most of the participants noted that these issues can affect education and employment function and cautioned their clients from using before or during work, or when starting a new position, as memory issues, motivation, and interaction with others can be negatively affected.

Four of the participants noted the potential for cannabis use to lead to a chronic habit or dependence. Unhealthy use patterns like “wake and bake” (starting the morning by getting high) may signal dependence. Two of the participants expressed some concerns about developing a psychological dependence themselves, such as habitual use in a situation where they felt like they should have refrained, or in using to calm themselves or help cope with stressful situations rather than utilizing other methods.

The authors discuss how the framework of rational choice can be utilized to examine these results. While the participants and their clients are aware of the risks or negative outcomes that can be associated with marijuana use, in the cost benefit analysis the benefits such as relaxation, mood enhancement, relief of anxiety, and pain relief outweigh the potential costs for both study participants and their clients as well. Indeed, few of the participants noted any negative outcomes from their use but they all held a comprehensive understanding of the potential risks. Interestingly, while there is some evidence of small physiological risk from marijuana use, only one of the participants mentioned the potential pulmonary or cardiovascular effects. However this may stem from a greater focus from the participants on the psychosocial aspects of use as it relates to their employment field. The study does provide evidence that legalization, acceptance, and use does not preclude mental health professions from recognizing the potential risks involved with marijuana use nor does it inhibit them from sharing that information and treating clients who may be struggling with use, abuse or dependence issues.

Ghelani, A. (2021). Cannabis Use Among Mental Health Professionals: A Qualitative Study of Cannabis-Related Risk Perceptions. Journal of Drug Issues, 51(4), 679-689

The Role of Context in Understanding the Use of Tactical Officers: A Brief Research Note

Jenkins, Semple & Bennell, International Journal of  Police Science & Management, 2021

The authors note that the use of tactical officers and services are being utilized more frequently in North America and in more incidents than in what is typically recognized as high risk incidents, like hostage taking, such as in proactive policing and warrant service. Some observers are concerned that these activities are disproportionally focused on minority communities. While the authors do give consideration to the view that the use of tactical police officers and services may not be called for in all instances, where they are used the authors contend that view often doesn’t consider the risk factors in those incidents that suggest the appropriateness and utility of those officers and services. They state that analyses of tactical operations use too often focuses on the type of call rather than the risk factors that may be present in the calls themselves. What might appear to be a relatively benign domestic disturbance type call may not account for risk factors like the violent or resistive history of the subject, situational factors like intoxication, and the presence of weapons. Feedback from tactical officers indicated these risk factors are typically in play in the calls that they respond to but these risk factors are typically not examined in studies of the use of tactical officers. The authors sought to use their current project to analyze more detailed contextual factors in the use of Canadian tactical officers. Using the same Winnipeg Police service data used in a previous study to suggest an increase in the use of tactical officers, the authors broke out the contextual data from the incidents to analyze the risk assessment for these types of situations. A coding scheme was setup and the four contextual risk factors analyzed were the history of the subject, (for example, their propensity of violence toward the police), the state of the individual, (for example, intoxication), the subject making threats to their own or others safety, and the belief that weapons were present, along with other contextual data contained in incident reports. Call type was also hierarchically coded to indicate the level of risk in the type of call.

Analyzing differences in the number of tactical responses between 2013 and 2016 indicated that a significant increase in deployment (from 474 in 2013 to 2757 in 2016) was more of a result in a change in reporting rather than change in their actual use. Data showed tactical officers responded to 78 different types of calls, though the vast majority (81% ) were reactive as opposed to planned operations. The most common calls tactical officers responded to were active warrant arrests, gun and weapons calls, shots fired, breaking and entering, domestics, alarm calls, suspicious persons, and well-being checks.

In regard to weapons believed to be on the scene, despite the variation in calls, on average, 60% of the calls indicated a weapon was involved, with more weapons present in the 2016 data than  in 2013. Of the weapons believed to be present firearms were mostly commonly reported in 2013 (42%) and in 2016 (48%). In the cases where additional information reported, call types that indicated a firearm was likely to be present on the scene, such as gun call, shots, fired, and gunshot wound, made up approximately half the calls where guns were thought to be present. However, of the calls in which a firearm was believed to be present, 59% of those calls were not firearm related. The authors state the findings suggest that simply looking at the call type is not a reliable indicator of the presence of weapons and suggests a variability of situations within call categories. It also appears that weapons are frequently believed to be present on seemingly benign calls like domestic disturbances, traffic incidents, and warrant executions, etc. With the concern over the use of tactical officers responding to “routine” calls the authors sought to determine how frequently firearms were believed to be present at some of these reportedly routine calls. The presence of firearms were believed to be present at 45% of suicidal threat and mental well being checks, as well as half of warrant executions and domestic disturbances, suggesting these are not low risk routine calls but actually pose a significant risk to officers and the public.

The other risk factor with enough additional information to be analyzed was the subjects’ history. Less information on the subject was available on reactive calls that tactical officers responded to (28% of tactical officer calls) versus planned operations (like warrant executions). The most frequently reported history risk factors in incidents were possessing weapons (8%), gang affiliations and previous murder or attempted murder charges (slightly greater than 1% for each). However 6% of calls also entailed the individual making explicit threats toward themselves, the public or  the police.

The research indicated that the majority of tactical officer responses were utilized in planned operation like warrant executions which entailed a variety of entry approaches from no-knock (approximately 1/3 of warrant executions), to knock and announce, knock and talk, or surround and call out, as well as being involved in subject takes downs and surveillance. Exploratory analysis between the roles of tactical officers and the belief that weapons were present on the scene, utilizing Chi Square, found a significant relationship. Specifically, knock and talk, and knock and announce, were used significantly more when no weapons were believed to be present compared to situations where firearms were believed to be present, while surround and call out and high risk takedowns were used significantly more when weapons were believed to be present. No knock entries were significantly more frequent when the belief that weapons were not present suggesting other factors, such as the likelihood of destroying evidence, contributed to that entry method, supported by the evidence that controlled drug and substance warrants made up nearly all the no knock warrants.

The authors conclude that a view that tactical officers are misused on routine calls, including warrant executions, and should be scaled back, misjudges the seemingly benign nature of these calls. Rather, the belief that weapons were present at the majority of these calls and that call type was generally not of indicative of the risk posed to the public or officers as the belief in weapons being present at supposedly low risk situations prompted the use of tactical officers. Thus the belief that a tactical response is unwarranted in routine calls may be a misguided view when this additional context is included. The authors did recognize that the limited contextual information in some call data prevents them from making policy recommendations but rather illustrates that contextual data is an important consideration in regard to making tactical police utilization and policy decisions. However this does require policing agencies to collect more detailed contextual information more frequently, in a standardized manner, in order to better assess the use of these officers and the policies recommendation  affecting their deployment.

Jenkins, B., Semple, T., Bennell, C., & Huey, L. (2021). The role of context in understanding the use of tactical officers: A brief research note. International Journal of Police Science & Management, 23(4), 385-391.

Welcome to Criminal Justice Access

Here’s what going on this month to start off your new year:

Interviews From the Field-Be sure to check out my interview with Steve Baker, a decorated 28 year veteran patrol officer, where he discusses patrol work, policing, the public, and the challenges facing police officers.

Research Briefs-Going back a few years this month with some articles you may have missed including an examination of legal challenges to fingerprint and DNA evidence, a more accurate way of determining the source of blood stains, discussing the development of a school shooter profile, factors contributing to deaths in law enforcement use of chokeholds, and the use of gaze tracking in officer shooting scenarios suggests a new approach to firearms training.

Original Research-Is there a difference between sociopaths, psychopaths, and people with anti-social personality disorder? How can they be recognized? Find out by checking out this academic examination of the issue in Differentiating and Diagnosing Sociopathy, Psychopathy, and Anti-Social Personality Disorder.

Research Briefs

Under the Microscope: Legal Challenges to Fingerprints and DNA as Methods of Forensic Identification

Wise, International Review of Law, Computers, & Technology, 2004

Wise discusses the advent of both fingerprint and DNA technology, and addresses the legal challenges they’ve faced as well as how the determination of legal validity will affect emerging biometric identification means. He notes that Galton, a 19th century scientist, proclaimed that fingerprints were unique to each individual and permanent, as well as developing a system to identify the unique characteristics of a fingerprint (called Galton points). Sir Edward Henry, a contemporary of Galton took an interest in fingerprints, and with consultation from Galton, developed the Henry Classification System to catalog fingerprint data, thus ushering in the modern era of fingerprint science The classification system is still used today and has enjoyed worldwide acceptance and use.

Challenges to the admissibility of latent prints are based on established standards of evidence admissibility. The 1923 case, Frye vs the United States, originally set a standard for expert testimony (in this case, in the admissibility of lie detector results), in that  experts should only testify if their testimony is based on “general acceptance” in the scientific community. This standard was widely utilized until the 1993 case, Daubert vs Merrel Dow Pharmaceuticals. This case set out new, comprehensive criteria which included, whether the scientific theory has been tested, whether it has been subject to peer review and publication, whether it has a known error rate, whether it has widespread acceptance, and whether there are operating standards. It was from the establishment of the Daubert standard that questions about the admissibility of latent prints arose.

In 1999, the case United States vs Byron Mitchell, was the first to challenge the admissibility of fingerprint evidence, and while the judge dismissed the challenge, the issue came up again in  2002, with United States vs Carlos Ivan Llera Plaza. The judge ruled that  while the analyst may testify to some components of the analysis such as the methodology and the number of matching points between the latent print evidence and the defendant, he would not be allowed to testify as to whether the evidence matched the print of the defendant. The judge ruled latent print analysis did not meet the Daubert standard, because of a lack of known error rate and differing standards on how many Galton points signifies a match. However, the judge later reversed his ruling after reviewing US and UK data, concluding that there was a clearly established standard of analysis in the scientific community to satisfy the Daubert standard. Since the Mitchell case there have been 40 challenges to the admissibility of latent print evidence but in all the cases, fingerprint evidence was allowed.

In 1984, Dr. Alec Jeffreys, a researcher studying gene structures determined that DNA sequences are unique to individuals and two years later was helping law enforcement utilize DNA to identify a serial killer in the UK., which both exonerated an innocent man and was able to match DNA from a suspect to the evidence. Jeffreys’ RFLP method has been refined since then to an STR technique where only a small amount of DNA is required for analysis, as well as developing the use of mitochondrial DNA testing that utilizes a different methodology that works especially well on degraded DNA evidence, and in cases requiring the identification of family members.

The first challenge to RFLP DNA evidence occurred in the late 80’s in the case of United States vs Bonds. The District Court ruled that the DNA evidence was admissible based on the “general acceptance” standard of Frye, however the US Court of Appeals ruled in 1993 that the DNA evidence was admissible under the Daubert standard, despite the laboratory not conducting external blind proficiency tests or referencing a known error rate. The judge determined that if the scientific community was accepting of  the technology, it must also then be accepting of the error rate as well. RFLP DNA analysis was also challenged in the NY case of the People vs Castro. In this case, the court used a three prong Frye test to determine if the theory, and its techniques and experiments, could produce reliable results that were generally accepted by the scientific community, and whether the laboratory performed the accepted scientific techniques in analyzing the sample in the particular case. The court ruled the first two prongs were met,, in that the science was sound, but that the laboratory failed to the meet the accepted scientific testing standards.

STR DNA analysis was also challenged in many courts. For example in State vs Traylor, although Traylor argued the validity of commercial DNA tests are unknown because of the use of proprietary regents used in the analysis, the MN Supreme Court, in 2003, ruled that the DNA Advisory Board and its established guidelines developed by the FBI, met the admissibility criteria and validated the science. While challenges to mtDNA are relatively new to the courts, recent challenges have established that mtDNA analysis  constitutes a “scientific knowledge based on reliable methods and principles”.

Newer DNA analysis technology, like Low Copy Number (LCN), while accepted, may face challenges as well. LCN DNA techniques can utilize very small samples of DNA and produce 17 billion copies to allow for analysis. However the concern is that as the original sample gets smaller in this process, any contamination in the sample will have a larger effect on the results of the analysis. Other concerns are the transfer of LCN DNA from casual contact and the lack of scientific evidence available as to how long this casual contact DNA could remain. While  “shedder indexes” are being investigated to determine the rate at which an individual donates potential DNA material (i.e. skin cells, hair, sweat), researchers have reported that DNA can be detected after transfer to an object for nearly three months in some cases and in one case for 2 years. Even more importantly, with such a small sample size of LCN DNA, there typically is no  material left over after testing for an outside source to run its own analysis and produce data. The FBI, with the exception of the limited application in human remains identification, remains skeptical of LCN DNA. Their official position is that any profiles obtained from LCN DNA should not be entered into the Combined DNA Index\System (CODIS) database of offenders and suspects. They also issued a caution against a rush to re-examine old cases on the hopes that LCN DNA would offer better analysis or change a verdict, mainly because of the risk of evidence contamination from repeated handling.

While fingerprints, and now DNA, are classic biometric measures, new measures of identification are being developed like ear prints, facial and voice recognition, iris, retina, and vein patterns, and hand geometry. The newer technologies will likely face challenges as they are introduced into the courtroom. Part of what drove the acceptance of latent print admissibility is that the scientific standard had been developed over a 100 years of use. Newer technologies will need to demonstrate that they can meet the Frye or Daubert standards and this also puts a burden on the judiciary, highlighting the situation created by Daubert,which requires judges, who are often not trained in the sciences, to act as gatekeepers of evidence admissibility. Even if these new technologies become “generally accepted”, criminal defense attorneys can still criticize the application of the method by the individual laboratory, and if the laboratory demonstrates they meet the scientific standards, the training or performance of the individual analyst can still be called into question.

Wise, J. (2004). Under the microscope: Legal challenges to fingerprints and DNA as methods of forensic identification. International Review of Law, Computers & Technology, 18(3), 425-434.

Recognizing the challenges faced in determining admissibility is important for defense attorneys as well as prosecutors, criminalists, and detectives. Being able to present solid, scientific based identifying evidence is crucial for prosecutions, as is producing accurate evidence data from other sources at the crime scene. Knock and Davison  developed a methodology that they believe will produced more detailed, accurate information on the source of blood stain evidence.

Predicting the Position of the Source of Blood Stains for Angled Impacts

Knock & Davison, Journal of Forensic Sciences, 2007

The authors note that in the field determining the source of blood splatter evidence  typically involves the “stringing method. As the authors explain “This technique uses the fact that the width to length ratio of a blood stain is approximately related to its impact angle. Using the calculated angle of impact, a straight line is drawn back from the stain along the line of the impact angle. Where the lines from several stains intersect is assumed to be the source of the stain.” They also note though that the effect of gravity on the flight path of blood droplets isn’t taken into account in making this determination. Knock and Davison experimented by dropping blood droplets of varying sizes at different height and angles against a hard surface. From this data, they produced one equation relating stain size to drop size and velocity for all impact angles, and a second equation, relating the number of spines (blood fingers extending from the center of the drop caused by impact) to drop size, velocity, and surface slope for all impact angles. The authors demonstrated that by combining these two equations, impact velocity can be accurately calculated and thus the true position of the blood stain’s source.

Knock, C., & Davison, M. (2007). Predicting the position of the source of blood stains for angled impacts. Journal of forensic sciences, 52(5), 1044-1049.

Revising and refining scientific methodology can improve the forensic investigative ability of detectives and criminalists but its also necessary to re-evaluate perceptions we hold about certain criminal activity and the perpetrators. Ferguson, et al reminds us that conventional wisdom is not always correct and that the analysis of data is necessary for the proper assessment of contributing and causal behavior in determining who might be at risk for perpetrating a school shooting.

Psychological Profiles of School Shooters: Positive Directions and One Big Wrong Turn

Ferguson, Coulson, & Barnett, Journal of Police Crisis Negotiations, 2011

The authors contend that the stereotype presented by the media and typologies produced both by the American Psychiatric Association and the FBI are simply inaccurate, or too overly broad and vague, to be of use. While conceding that first hand data from shooters who often die in the incident is hard to come by, a more evidence based typology can be utilized.

School shooters are typically portrayed as loners, involved in the Goth subculture or other out-groups, who enjoy violent video games, were bullied, and had disruptive or negligent home lives. When school shootings increased in the’90’s the public, academics, politicians, and activists demanded answers, despite their relative rarity and the overall general decline of youth violence.

In 1999, the FBI provided a threat assessment profile for school shooters cautioning against its use other than in assessing the credibility of a threat already made by an individual. Some criteria seem reasonable like “injustice collector, dehumanizes others, and lacks empathy” while others were vague in definition like an “unreasonable interest in sensational violence” and overly broad like “a failed love relationship, a sense of superiority, exaggerated need for attention, externalizes blame, closed social group, a fascination with violence filled entertainment”.

As of 2010 the APA maintained a warning signs list for serious youth violence including obvious signs like “enjoying hurting animals, detailed plans to commit acts of violence, and announcing threats or plans for hurting others” but like the FBI’s threat assessment, others are vague in definition like “frequent physical fighting” while others could apply to great numbers of mentally-well juveniles like, “feeling rejected or alone, poor school performance, and access to or a fascination with weapons, especially firearms”.as well as including ideas that have been discredited by research like “violence is a learned behavior” and linking violent media, like video games, with violent behavior.

These attempts at recognizing school shooters will result in over-identification and misidentification and while empirical evidence on characteristics of school shooters is scant, a 2002 report from the Secret Service and Dept. of Education does provide a more data derived (albeit descriptive) picture of school shooters. The reported analyzed 37 attacks, involving 41 perpetrators from 1974 to 2000 and utilized school and court records, mental health and legal documents as well as interviews with the ten surviving perpetrators. The report made clear that with the wide difference among perpetrators that no profile for school shooters existed, though there were some features that tended to be more widespread. The report also demonstrated that the stereotypical school shooter image is inaccurate. The SS/DOE report found that video game playing was relatively low, only 15% expressed “some interest in violent video games” and just 59% expressed “some interest in violent media in other forms”, with the authors noting these figures are lower than those found for non-shooter males in other studies. However, 37% were exposed to media violence through their own poems, essays, and journals.

Social isolation was not found to be common with school shooters. Most had friends, 41% belonged to a mainstream social groups, (27% were part of fringe groups but also had friends). In categories that were not mutually exclusive, only 12% had no friends and 34% were described as loners. School and family background also did not figure prominently into school shooters’ behaviors. However mental health issues were a factor. 98% of perpetrators experienced some kind of major loss right before the incident, 78% had a history of suicide attempts or ideation, 71% percent of then perceived themselves as wronged, bullied, or persecuted by others, and 61% had a documented history of significant depression. However very few of the perpetrators had received any mental health care in the past, suggesting a failure of our mental health system that has contributed to these incidents, Two prominent warning signs noted in the SS/DOE report were that 81% of perpetrators warned an uninvolved person prior to the attack and that 93% had already engaged in behaviors that alarmed peers, teachers, parents, or mental health professionals.

These factors have been identified in research on adult perpetrators of mass homicide as well as figuring into youth violence in general. Ferguson noted his upcoming study revealed that violent media was not a factor in youth violence, however current levels of depressive symptoms coupled with antisocial personality traits, were highly predictive of youth violence. The authors suggest that reducing school shootings should focus on preventative measures however, reform in addressing mental health needs is long overdue, and funding for adequate at-risk youth and adults services will be slow in coming. They also note that because of the likelihood that perpetrators may signal their violent intent before the action, that prevention can take the form of peers acting upon what they hear or see and informing law enforcement or school officials.

Ferguson, C. J., Coulson, M., & Barnett, J. (2011). Psychological profiles of school shooters: Positive directions and one big wrong turn. Journal of Police Crisis Negotiations, 11(2), 141-158.

Officers are often called upon to confront resistant and/or violent individuals and by necessity have a choice of non-lethal options they can employ in these encounters. One technique that has caused controversy over its application and the potential for harm to suspects is the chokehold, both historically and as recently as last year. Below, Dr. Koiwai examines factors that may be contributing to deaths in the application of choke holds.

Deaths Allegedly Caused by the Use of “Choke Holds” (Shime-Waza)

Koiwai, Journal of Forensic Sciences, 1987

Author Koiwai, MD, stated that the chokehold technique used by police officers is the same chokehold (Shime-Waze) used in Judo. Yet while officers have been involved in the deaths of suspects following application of the hold, Koiwai notes that since the sport of Judo was established in 1882, there have been no fatalities associated with the use of the hold in Judo.

Koiwai briefly discusses the control techniques used by the police which are similar to Judo chokeholds, including the carotid control hold (fig. 1) the locked carotid control hold (fig 2), as well as the bar arm control hold, where the left hand is placed on the back of the subject’s head forcing it down. All of these holds are finished by using the hold to take the subject down to a seated position and applying the hold until the subject becomes unconscious or ceases resisting.

Koiwai examined the autopsy reports of 13 cases between 1975-1985 which involved a law enforcement chokehold being applied. The decedents were males, Black and White, between the ages of 19 and 58, though the majority were under 40, and their weight ranged from 120-220 pounds, though in only one case did the decedent weigh over 170 pounds. While in all but one case the decedents were violently resisting arrest, which necessitated the use of the chokehold, the case narratives indicate that in six of the cases, the decedents were very violent and combative. In three of the 13 cases, acute intoxication from alcohol or drugs was involved, two other cases involved decedents suffering from psychosis, as well as the findings that in three other cases, pre-existing heart conditions contributed to the death. In almost all the cases medical attention was provided in a timely matter, though in all the cases, asphyxiation was a primary factor, including in some cases, aspiration of vomit, and brain death from oxygen deprivation.

In all 13 cases, the author noted evidence of injuries to the structures of the neck ranging from bruises, lacerations, hemorrhages, and vascular compression, as well as fractures of the cartilage of the neck in five cases, and intervertebral discs in one case. Submucosal or mucosae injuries are noted in the larynx in five cases. All these findings indicate that tremendous force was exerted on the necks of the decedents. Koiwai noted that only a relatively small amount of pressure is necessary to close off the carotid arteries and that unconsciousness should occur in only 10-20 seconds, with regaining consciousness occurring in about the same time length. Koiwai stated that the force applied to collapse the airway, as occurred in these cases, is 6 times greater than necessary to effectively apply a chokehold, which resulted in the injuries seen in the autopsy reports. Properly applied the chokehold puts pressure on the superior carotid triangle, closing off the carotid artery but leaving the vertebral artery unobstructed. (fig 5) Completely obstructing the blood flow to the brain or asphyxia by closure of the trachea can lead to irreversible damage or death.

Koiwai suggests that police department training manuals should emphasize that control holds should be used only when necessary to stop a suspect’s resistance and not necessarily to cause unconsciousness. If police officers are to use the choke holds to subdue violent suspects as a last resort, they should be properly trained and supervised by trained, certified judo instructors to ensure that there will be less misuse or abuse of the technique which when used improperly results in fatalities. These fatalities could be reduced if (1) choke holds are taught by trained and certified instructors (2) if officers become familiar with the anatomical structures of the neck and where the pressure is  to be applied (carotid triangle), (3) if they understand the physiology of choking, in that only a small amount of pressure is needed to cause unconsciousness; (4) if officers are taught to recognize immediately the state of unconsciousness and to release the pressure immediately, (5) learn proper resuscitation methods if unconsciousness is prolonged; and to prevent the aspiration of vomit and not to place the restrained suspect face down, (6) and keep the subject under constant observation. (7) Additionally, police training manuals should be revised to emphasize the above procedures and principles, all of which will prevent deaths from chokeholds.

Koiwai, E. K. (1987). Deaths allegedly caused by the use of “choke holds”(shime-waza). Journal of Forensic Science, 32(2), 419-432.

Police officers face challenges in recognizing when to apply force and the level of force itself. Proper training in different techniques makes for better, more professional officers, as well as decreased injuries and fatalities for suspects. However, having a means to assess officer performance when they face potentially violent encounters is crucial to understanding their behavior and decision making in those encounters. Those observations can then be used to improve officer performance and public safety as well. Vickers and Lewinski examine the differences between elite and rookie police officers in their preparation for use of a firearm in a violent confrontation.

Performing under pressure: Gaze control, decision making and shooting performance of elite and rookie police officers

Vickers & Lewinski, Human Movement Science, 2011

The authors discuss that currently most firearms training programs teach officers to focus their gaze on two locations, first on the sights of their gun, and secondly on the target before pulling the trigger. This gaze strategy works very well in training with rookies achieving high accuracy scores in initial firearms training, but once on the street and faced with a violent firearms encounter they shoot poorly, averaging between 10 and 60% accuracy. The high pressure states that shooters face tend to cause more visual fixations of a shorter duration and reduced ability to detect peripheral information.

When elite shooting athletes were studied they found that they tended to fixate on the target, and kept that sight gaze as they aligned their firearm sights with the target, rather than switching gaze from sights to target; this allowed for a longer final fixation on the target leading to greater accuracy, and the reduction of pressure, anxiety and psychological stress. The authors tested 11 elite Emergency Response Team members and 13 rookie officers nearing the end of their training period, with gaze tracking software, putting them in a role-playing scenario where they are informed a threat may appear in the area they are monitoring. An upset male enters the location and becomes increasing agitated with an individual playing the role of a receptionist. In the final two seconds of the encounter, the male quickly pivots and draws on the officer who is seven yards behind him, drawing either a gun or a cellphone. Officers were assessed on their gaze duration, gaze location, amount of gaze shifting, speed, accuracy and locations of shots fired, time involved in the unholstering, draw, aim, and fire phases, and the rate that they inhibited firing in the cellphone scenario.

Following data analysis, statistically significant differences were revealed.

  Elite Officers Rookie Officers
Hit on assailant 74.5 % 53.9 %
Decision making (fired on cellphone) 12.3 % 61.5 %
Fired before assailant 92.5 % 42.2%
High Performance (meeting all above criteria) 75.0 % 52.9 %
Fixated on more locations where gun could be concealed 50.3 % 30.6 %
Fixated on locations where gun couldn’t be concealed 42.1 % 51.1 %
Fixated on areas off the assailant 7.6 % 18.1 %
Unholstered weapon after assailant entered 1.77 sec. avg 6.28 sec. avg.

Statistically significant differences were also found in the final phases of the scenario between the onset times of the different phases based on officer status.

Onset Elite Rookie
Draw 4.63 sec. 6.04 sec.
Hold 4.81 sec. 6.26 sec.
Aim 5.83 sec. 6.36 sec.
Fire 6.87 sec. 6.93 sec.

There were also statistically significant differences between elite and rookie officers in their visual fixations during the final two seconds of the scenario.

Fixations Elite Rookie
Increased visual fixation on assailant weapon From 18 % to 71 % From 18 % to 34 %
Decreased fixation on non-weapon locations From 78 % to 7 % From 62 % to 16 %
Increased fixation on officer’s weapon to 20 % 39 %
Fixations off assailant 4 % 13 %
Final fixation on officer weapon not assailant 32% 84 %
Final fixation time on assailant  before firing .32 sec. .27 sec
Final fixation time on ofcr. weapon before firing .12 sec .24 sec

In reacting to the threat, rookie officers performed the final phase actions in the last second of the scenario versus elite officers who performed the actions in the last 2.5 seconds, starting the process earlier, taking more time to focus on the assailant and less time focusing on their own weapon. The elite officers’ earlier draw was also preceded by more time spent focusing on assailant weapon locations than rookies. Elite officers maintained more visual focus, drew sooner than rookies in anticipation of the threat, and thus gave themselves more time in the final aim and fire phases for increased fixation focus, which accounted for their better hit and discrimination rates. The authors stated that their results suggest that firearms training should change from a process that inadvertently teaches rookies to fixate on the sights of their own weapon first and the target second, to a type of training that establishes the line of gaze on the target from the outset, followed by alignment of the sights of the weapon to the line of gaze. This change in gaze control would lead to a longer final visual fixation duration on the target prior to pulling the trigger and should contribute to better decision making and performance. If these changes in firearm’s training were implemented, then the gaze control of novice officers should be similar to that of elite athletes and elite officers from the first day of training, which should decrease errors in decision making and improve shooting accuracy.

Vickers, J. N., & Lewinski, W. (2012). Performing under pressure: Gaze control, decision making and shooting performance of elite and rookie police officers. Human movement science, 31(1), 101-117.