Document Category: Expert Testimony

This brief argues that funding for and admission of an antiracism expert witness is necessary to ensure due process and fairness under both the U.S. and Massachusetts Constitutions, as well as Mass. Gen. Laws ch. 261, § 27C. An antiracism expert’s testimony would assist the factfinder in understanding how structural and interpersonal racism shape perceptions, witness credibility, and evidentiary interpretation—areas outside common experience. Citing Professor Jasmine Gonzalez Rose’s work on “implicit judicial notice,” the brief explains that judges and jurors often unconsciously apply white-normative standards to assess evidence, producing an unequal evidentiary burden for defendants of color. Expert testimony mitigates this bias by contextualizing how race influences policing, charging, and factfinding. The brief grounds admissibility in Mass. G. Evid. § 702 and related case law. It further relies on due process cases to establish that indigent people have a constitutional right to necessary expert assistance. Defenders can use this brief to support motions seeking appointment and funding of experts on race, bias, cross-racial identification, etc. in Massachusetts and other jurisdictions.

This motion argues that evidence of a client’s alleged substance use must be excluded because it constitutes impermissible character evidence under FRE 404(a), poses a high risk of unfair prejudice under FRE 403, and invites unqualified medical opinion testimony in violation of FRE 701. Citing social-science research showing that jurors associate substance use with immorality, violence, and dishonesty, the motion argues that such evidence leads jurors to condemn defendants based on stigma rather than proof of guilt, rendering the evidence unfairly prejudicial. Finally, it explains that terms such as “addict,” “dependence,” and “abuse” describe medical diagnoses that only qualified experts may offer, rendering lay testimony about addiction inadmissible.

This motion seeks exclusion of firearm and toolmark identification evidence under Daubert and Michigan Rule of Evidence 702, arguing that the AFTE method lacks foundational scientific validity and relies on subjective, unarticulated examiner judgment. Drawing on the National Academy of Sciences and President’s Council of Advisors on Science and Technology reports, the motion explains that the field lacks standardized protocols, reproducible methods, and reliable error rates, with some studies documenting false positive rates as high as 11.2 percent. The motion further argues that such evidence misleads jurors by cloaking opinion testimony as scientific and should also be excluded under Rule 403. Defenders can use this motion to demand Daubert hearings, limit examiner testimony, or seek outright exclusion of firearm and toolmark evidence.

This motion describes social science research about the fallibility of fingerprint evidence (pp. 1-6); explains that jurors tend to perceive fingerprint evidence as infallible and over-rely on it (pp. 6-7); and discusses the effectiveness of jury instructions in countering this preconception of infallibility (pp. 7-15). The motion describes, links to, and argues for a short informational video that research shows enables jurors to evaluate fingerprint evidence properly (pp. 8-10). It also argues for a reason-based jury instruction with specific factors for jurors to consider when deciding how much weight to give fingerprint testimony (pp. 12-19).

This motion challenges a forensic child abuse investigator’s attempt to bolster a child complainant’s credibility in a sexual assault case through testimony about Child Sexual Abuse Accommodation Syndrome (CSAAS). Drawing on social science and precedent, the motion argues that CSAAS testimony is not admissible under FRE 702 & Daubert because it is not scientifically reliable (pp. 15-19), has not been tested or subjected to peer review (pp. 19-24), and is not generally accepted (pp. 24-27). The danger of unfair prejudice also substantially outweighs any probative value such that it is inadmissible under FRE 403 (pp. 35-38), and CSAAS testimony is not helpful and improperly invades the jury’s province to determine witness credibility (pp. 38-40). The motion applies to testimony by a forensic examiner about alleged common responses of child sexual assault victims to abuse, including secrecy, helplessness, accommodation, delayed disclosure, and recantation (pp. 32-33).

This draft motion relies on social science about the effectiveness of mental imagery techniques at combatting implicit biases to argue for a proposed criminal jury instruction that employs a “cloaking” or “perspective-switching” exercise in which jurors are asked to consider if their impressions of the defendant (or a witness) would change if they were a different race. The draft motion collects research showing how pervasive implicit racial bias is, how voir dire alone is ineffective at ensuring defendants get fair trials, and how effective mental imagery exercises can be.  It also explains how other jurisdictions already have mental imagery instructions.

This motion argues for the exclusion of opinion testimony by medical examiners on the manner of death in a homicide trial under both the rules of evidence and the Sixth Amendment jury trial right. It explains that medical examiners speculate as to the “manner” of death based on extraneous information provided to them, notes that these determinations are not based on science, and emphasizes that there is “no standardized or validated system” for making these judgments (pages 18-23). The motion also cites cognitive science in support of the claim that biases, including racial biases, can shape these “manner of death” determinations (pages 23-24). Attached to the motion are (1) transcripts of interviews with two medical examiners, exposing the problems with manner of death determinations; (2) an expert report and law review article detailing the cognitive science problems with these determinations; (3) the non-scientific manual used to instruct medical examiners on how to make these determinations; and (4) a letter signed by 86 forensic pathologists and death investigators about judicial misuse of manner of death determinations.

This motion challenges the scientific reliability of a prosecution expert’s testimony related to AHT/SBS. The motion outlines the history of AHT/SBS (pp. 11-15), details why AHT/SBS is not a scientifically reliable diagnosis, and applies the Daubert and Federal Advisory Committee Notes factors to AHT/SBS (pp. 29-33). The motion details how biomechanics undermine the premise of AHT/SBS (pp. 16-20), points to studies that demonstrate that children can in fact die from short accidental falls (pp. 19-20), and explains how the triad used to diagnose AHT/SBS can have non-abusive causes (pp. 21-26).

This motion relies on the Federal Rules of Evidence to argue for exclusion of expert DNA testimony about the likelihood ratio obtained using STRMix probabilistic genotyping software. Pages 5-8 describe the basic steps of DNA extraction and analysis. Pages 8-9 discuss the problems of trace DNA and the possibility of innocent transfer of DNA.  Page 11 explains how DNA analysis is less reliable when there is a complex DNA mixture and pages 12-15 discuss the danger that jurors will misunderstand (and prosecutors will misrepresent) what a likelihood ratio actually means.

This motion relies on the Federal Rules of Evidence to argue for exclusion of police testimony about the behavior of drug traffickers. Pages 13-14 rely on social science to argue that users of fentanyl, methamphetamine, and cocaine consume large quantities of each of those drugs daily to support their habit such that courts cannot infer distribution from larger amounts. Pages 15-16 collect national data to refute the suggestion that drug traffickers typically possess firearms.

This brief explains why expert testimony on firearm and toolmark (FA/TM) identification should be excluded. FA/TM identification is premised on the unproven assumption that each firearm leaves unique, accidental, and individualized markings on spent ammunition despite evidence from several studies that this analysis lacks sound estimates of error rates, is characterized as subjective pathological science, and is not based on reliable scientific principles. This brief collects empirical studies and evidence demonstrating that FA/TM identification lacks scientific validity (pp. 14-22), and it explains the methodological problems and high error rates associated with various studies used to attempt to validate FA/TM identification (pp. 22-43). Because of the imprecise and problematic nature of FA/TM identification, the brief also contends that experts should not be allowed to testify about characteristics of spent ammunition that imply a match (pp. 49-59).

This motion relies on social science demonstrating the unreliability of witness attempts to identify people from surveillance videos/photographs and argues that due process and the evidence rules (Rules 602, 701, and 403) require exclusion of a police officer’s attempt to identify the defendant from a surveillance video.

Pages 2-4:  Discuss studies showing that humans are bad at matching people to images in photos/videos

Pages 4 –9:  Discuss studies showing that image quality (resolution, distance from subject, and moving versus still images), camera angle and viewpoint, lighting conditions at the time of the video or image capture, the presence or absence of obstructions to the camera’s view, and the size of the image captured all affect reliability

Pages 9 – 13: Discuss how situational factors including a lack of prior familiarity, cross-racial identification problems, and time delays between a prior exposure and the viewing of a surveillance photo/video all contribute to mistaken non-eyewitness identifications

Pages 15-16 – Discuss how these studies could also be used to (a) limit or prevent the prosecution from asking the judge/jury to compare a surveillance video/photo to the defendant, (b) obtain favorable expert testimony about the problems of non-eyewitness identification; (c) get the court to take judicial notice of these problems; (d) obtain favorable jury instructions about the problems with non-eyewitness identification testimony; (e) cross-examine non-eyewitnesses more effectively.

Draft motion arguing that finding many grams of methamphetamines does not necessarily support a conviction for possession with intent to distribute. Bottom of p. 1 through p. 3 explains that people addicted to methamphetamines use more frequently and in higher dosages than first-time users, using as much as one gram per day and rarely (but at least once) up to 15g in one day. Thus a person found with many grams of meth may only be a user rather than a dealer.  This data could also be used in other arguments, including: (1) a suppression argument that there is no probable cause to search a location for evidence of distribution when the quantity recovered or known about only suggests personal use; (2) a Rule of Evidence 403 argument limiting the testimony of a witness who wants to characterize a given quantity of meth as “a lot of drugs” or who wants to describe the client as a drug dealer or distributor; (3) a sentencing argument that a client is not as much of a danger to their community as someone actively selling drugs, despite the amount of drugs found.

This draft motion section relies on psychological and neuroscientific research to argue that young people who have been exposed to trauma behave differently when interrogated and are more likely to give false, unreliable, and involuntary confessions such that past exposure to trauma should be an important factor in the voluntariness analysis.

Pages 2-3:  Youth with trauma histories are quicker to perceive subtle threats from interrogators.

Pages 3-4: They are more sensitive to environmental stressors

Pages 4-5:  They are more distressed when they perceive threats leading to over- and under-reactions

Pages 5-6:  They often give in to authority figures and confess to avoid additional trauma

Pages 6-7:  They are more susceptible to police interrogation tactics like maximization and minimization.

Pages 7-11:  These pages discuss other potential uses of this emerging research, including (a) a request for funding to retain an expert to explain how a client’s trauma symptomatology may have manifested during an interrogation; (b) arguments that prior trauma exposure should be considered when determining whether an adolescent was in custody and being interrogated; and (c) arguments that prior trauma may affect the voluntariness of a Miranda waiver.

The ACLU of Michigan included these reports as exhibits in its recent litigation attacking the constitutionality of Michigan’s Sex Offenders Registration Act (SORA). Does v. Whitmer (Does III), No. 22-cv-10209 (E.D. Mich.). The research cited in these reports — specifically on the low risk of recidivism among people convicted of sexual offenses and the counterproductive impact of registration/notification requirements on public safety and recidivism — could be used (1) when negotiating with a prosecutor for a plea to a non-registration offense, (2) when justifying such a plea to a sentencing judge, (3) in pre-trial release arguments, (4) in sentencing arguments where clients will be forced to register to show the onerous nature of registration, or (5) to support a motion in limine to preclude reference to a client as a “sex offender.”

(Note that the following page numbers are keyed to the page numbers in each expert report, which you can find in the middle bottom footer of each report):

Letourneau Report

Pages 2-11: Explaining through a dozen different scientific studies that sex offender registration and notification laws fail to increase community safety, do not have a general deterrent effect, and may even increase the incidence of crime by making it difficult for ex-offenders to find and maintain housing, employment, and social relationships.

Pages 11-12: Noting that researchers have found no connection between juvenile registration/notification and an increase in public safety but they have found increased incidences of attempted suicide among juvenile registrants as well as an increase in their likelihood of being victims of sexual assault themselves.

Pages 12-13: Citing research showing that 80% to 90% of adult males convicted of sex offenses are never reconvicted of a new sexual crime, including studies that debunk recidivism myths by showing rates of recidivism as low as 2-5%.

Pages 13-14: Discussing research showing that conviction offense has no bearing on recidivism risk.

Pages 16-17: Citing research showing the negative impact of registration on people’s mental health and ability to find and maintain stable housing, employment, and prosocial relationships, creating barriers for reintegration.

Pages 17-20: Discussing why the costs of implementing sex offender registration and notification laws are greater than any savings or benefits generated by those laws

Pages 21-22: Finding no correlation between failure-to-register violations and sexual recidivism

Socia Report

Pages 4-8:  Citing research showing that 90-95% of all sex crime arrests are for first-time offenders; the vast majority of sex crimes are not committed by strangers; and sex offender registration and notification laws do not reduce recidivism or make communities safer

Page 9-12:  Debunking through scientific research any suggestion that there is a high sexual recidivism rate and noting that sexual recidivism rates are actually lower than those of any other offense except murder

Pages 16-17:  Noting that language matters to public perceptions and that individuals are more likely to think negatively about someone described as a “sex offender” than someone described as an “individual convicted of crimes of a sexual nature” (this research might support a motion in limine about how clients should be described in court)

Pages 19-22:  Documenting how individuals on the sex offender registry are stigmatized in ways that affect reintegration including compromising employment and housing opportunities, as well as social support networks

Pages 22-25:  Noting that there is no consistent evidence that failure-to-register convictions predict increased sexual recidivism.

Amicus brief, filed by a coalition of gender justice organizations, explains how sexual and gender-based trauma has profound adverse impacts on mental health, leaving survivors vulnerable to PTSD, depression, anxiety, emotional numbness, substance use, and revictimization (pp. 3, 5, 7, 13–15). Childhood sexual abuse increases susceptibility to these harms and can disrupt brain development (pp. 9–11). Trauma is cumulative—repeated exposure intensifies risk (pp. 11–12). The brief highlights that sex workers are at significantly higher risk of sexual violence (p. 15). Mitigation evidence related to gender-based trauma is crucial to countering social biases and prejudices of decision makers (pp. 20, 23, 25–26). While the brief focuses on capital sentencing, defenders can also rely on its research to support requests for gender and sexual violence experts and for sentencing mitigation.

This brief argues that, contrary to stereotypes, drug use alone—even frequent or illicit use—does not necessarily indicate substance abuse (pp. 23, 28-29). Only a minority of users develop a diagnosable SUD (p. 23). A single positive drug test is insufficient to establish a SUD (p. 29). And equating substance use, even a SUD, with substantial risk of harm to a child is unsupported by the medical evidence (pp. 40-42).  Defenders can use the research collected in this brief to file motions in limine to exclude evidence of or arguments about substance use as more prejudicial than probative or to obtain expert testimony on substance use.  The research could also be useful at the pretrial release and sentencing stages to suggest that clients do not suffer from a substance abuse disorder and do not pose a danger.

p. 40-86 outline the flaws in firearm identification, the current state of the field, and issues of cognitive bias

Pg. 13 – noting that there is no reliable scientific study validating the hypothesis that shaking alone can cause bleeding in the brain and eyes and neurological impairment; accidents can cause these symptoms

Pg. 14 – discussing thirty documented exonerations of innocent people wrongfully convicted based on shaken baby syndrome (and in 13% of those cases, the innocent person falsely confessed)

Pg. 19 – discussing a survey that reveals fewer than half of forensic pathologists think SBS is a valid diagnosis

Pgs. 20-28 – discussing why experts in biomechanical engineering are relevant to and regularly testify in SBS/AHT cases and how biomechanical studies show that shaking alone cannot produce the medical findings associated with SBS/AHT

Pgs. 28-31 – discussing the many non-abusive causes/circumstances that can present the same diagnostic signs relied upon to support SBS/AHT

Pgs. 38- 39 – collecting research that discusses the biasing impact of false confessions, how they corrode evidence collection and create a false appearance of corroboration, and how likely they are to lead to erroneous convictions

Pgs. 39-40 – documenting the problem of contaminated confessions

Pgs. 41-42 – discussing research showing that (a) individuals who have experienced trauma as well as (b) individuals who are depressed are more susceptible to police coercion and more likely to falsely confess

Pgs. 42-44 – discussing research about the dangers of police reliance on false evidence ploys to induce confessions

Pgs. 48-50 – surveying recent social science evidence on false confessions

Pgs. 50-53 – discussing social science research on confirmation biases in forensics

This brief follows an extensive Frye hearing on bullet matching evidence and incorporates extensive criticism from the scientific community, an explanation of the unintended impact that a narrow definition of the “relevant scientific community” can have, and evidence of the ways that cognitive bias impermissibly taint pattern-matching evidence.

Pgs. 7-8 – summarize scientific research describing how people create entirely false memories, a study of false memory creation, and a list of false memory risk factors, particularly for children.

Pgs. 9-10 – explain how interview techniques can create false memories in children, even false memories that do not seem to directly relate to the questions asked by the interviewer, and why expert testimony is needed to educate the jury on the counterintuitive nature of memory creation (i.e., the more detailed a memory, the higher the likelihood of error).

Pgs. 12-14 argue that, because the science behind false memories is similar to that of mistaken eyewitness identifications and both require jury education to evaluate witness credibility, expert testimony on false memories should be admitted at the discretion of the trial judge under the same logic.

p. 35-65 detail research demonstrating bite-mark comparison has “no empirical support” high error rates, and is not accepted within the scientific community

This motion relies on federal rules of evidence and Daubert to argue that a physician should not be permitted to testify that a person died from an oxycodone overdose when there are alternative potential causes of death – such as cardiac arrhythmia – that have not be properly eliminated. More generally, the motion explains when doctors who rely on differential diagnosis – the process of identifying the cause of a medical problem by eliminating likely causes until the most probable one is isolated – are conducting a reliable, medical analysis versus when their analyses are compromised by cognitive biases. The social science collected in this motion would be useful to defenders challenging the validity of any causal conclusion physicians reach.

Pages 4-6 explain the differential diagnosis process and how it can lead physicians to make unreliable conclusions about cause of death.  Pages 6-17 discuss how cognitive biases like confirmation bias, role effects, the availability heuristic, and the representativeness error can infect differential diagnoses.  Pages 17-20 talk about when differential diagnoses are unreliable due to a physician’s failure to properly rule in certain causes and rule out potential alternatives.  Pages 20-24 draw analogies to the forensic sciences and argue that the physician in this case could testify that there was oxycodone in the patient’s system but should not have been able to opine with certainty that it caused the patient’s death.  Pages 24-28 explain why the doctor’s ultimate opinion invaded the province of and was unhelpful to the jury.

Pages 1-4 discuss the history and development of the DRE program; pages 6-10 explain how the DRE test fails Rule of Evidence 702 because it does not assist the trier of fact to understand a fact in issue and the officers who testify about it are not qualified in the relevant field of knowledge; and pages 11-26 explain why the DRE protocol fails each of the five Daubert factors.

P. 21-25 of the brief details the developments in scientific understanding of fire, including the 2004 National Fire Protection Association’s Guide for Fire and Explosion Investigations (NFPA 921), studies conducted by ATF and the National Institute of Justice, and other experts.

p. 22-33 explain the changing landscape of arson investigations and wide-scale rejection of the “negative corpus” theory that some fire investigations rely upon.

Filed by the Center for Integrity in Forensic Science, this brief explains the research demonstrating that cognitive bias in forensic analysts contributes to unreliable conclusions.

Focusing on retinal hemorrhages, this motion cites research showing no proven correlation between shaking and retinal hemorrhage, as well as studies documenting other (non-shaking) causes of retinal hemorrhage.

Overview of flaws in proposed testimony explaining how children respond in aftermath of sexual abuse

This expert report collects and describes cutting edge social science describing the problems with eyewitness identifications including: the effects of poor lighting and distance (p. 5); the effects of a quick exposure and the problem of witnesses’ overestimating the length of exposure (p. 5-6); problems with cross-racial identifications (p. 6); problem if witness previously viewed the person in another context (unconscious transference) (p. 7); problem of memory loss over time (p. 7); suggestive instructions & failure to warn that culprit may not be in line up (p. 8); problems with nonblind lineup administration (pp. 8-9); problems with biased lineup composition (bad fillers) (p. 9); what can be learned from how long it takes witness to make ID (p. 10); problems with in court identifications (commitment effect and inherent suggestiveness) (pp. 10-11); problems with witnesses being overconfident about IDs (pp. 11-12)

Details risk factors for false confessions, benefits of a defense expert on false confessions, and why expert testimony on false confessions satisfies Daubert

Filed by the Innocence Project, this brief details research demonstrating that hair microscopy evidence does not meet the standards of reliable scientific evidence, as well as research showing how persuasive forensic testimony is to juries.

Based on forensic reports on latent fingerprint matching, this motion argues that fingerprint analysts can only accurately testify in terms of exclusion, rather than that two prints are a “match,” from a “common source,” or that any individual is “the source” of a latent fingerprint.

This brief challenges a police officer’s testimony opining that a shooter pictured in surveillance footage and the defendant were the same height.  The officer based his opinion on his visual observation of surveillance footage and measurements of the height of markings in the store. The Florida appellate court agreed that this was impermissible lay opinion testimony that invaded the province of the jury and required specialized expertise (https://caselaw.findlaw.com/court/fl-district-court-of-appeal/2076011.html).

Pages 17 – 23:  Discuss the science of photogrammetry – the process of discerning the size of objects in a photograph – and explain how estimates of an individual’s height in a photograph or video require expert calculations based on geometry, physics, and photogrammetric triangulation.  As a result, the brief argues that only a qualified expert can opine about the height of an individual in a photo or video, and a police officer’s opinion based on visual observation of the photos/video is unreliable, untethered from science, and inadmissible under both due process and evidentiary rules.

Testimony of defense expert on issues surrounding Shaken Baby Syndrome diagnoses

Summarizes research on accuracy of “criminal profiling” evidence over forty years, concluding profilers are no “better than bartenders at predicting the traits and features of offenders.” Also provides an overview of cases nationwide excluding criminal profiling evidence and finding that its major premise is faulty and essentially propensity evidence.

Report overviews existing research on false confessions and specific risk factors for false confessions.

Transcript of testimony and argument pursuant to the defense motion to exclude the government’s expert witness. Defense witness explains (with research studies as examples) confirmation bias, contextual bias, and exposure to task-irrelevant information. Arguments: p. 57-70.

Argues “substantial amount[s] of highly inflammatory task-irrelevant context information,” improperly impacts opinions, cites research on contextual bias in forensic experts

Witness testifies about confirmation bias, clothing bias, witness degree of certainty, police witness accuracy, and face-to-photo ID accuracy

p. 36 – 94 contain testimony about shortcomings of latent print identification

Transcript of defense expert witness testimony focusing on contextual bias in forensics.

Details the flaws in Bloodstain Pattern Analysis, the lack of enforced standards, and the high error rate. Additionally explains the danger of contextual bias impacting the decision of forensic analysts.

p. 11-15 overview reliability issues with fire investigations, particularly the lack of measurable standards and verifiable data.

p. 10-12 discuss a study that found that people with normal smell identification abilities could only smell a 5-pound bag of marijuana in a trunk 13% of the time, and that 10% of the time people thought they smelled marijuana when there was none. p. 12-13 argues that an officer can impermissibly taint a search by suggesting that he smells marijuana, similar to tainting a lineup by suggesting the suspect to the witness.

Argues that gunshot residue evidence is not reliable

Explains process of latent fingerprint analysis, lack of uniform standards, false claims of “absolute certainty,” and why fingerprint analysis fails the Daubert standard.

p. 8-12 incorporate social science studies on how jurors respond to testimony designated as “expert”

Explains history of the ACE-V method, the risk of confirmation bias, and the lack of uniform standards in fingerprint matching.

Overviews shortcomings in firearm/toolmark analysis, specifically argues against any testimony of a “match”