Mock Juror Perceptions of Forensics

This CSAFE Center Wide webinar was presented on December 8, 2020 by:

Brandon Garrett – L. Neil Williams Professor of Law, Faculty Director at the Wilson Center for Science and Justice

Nicholas Scurich – Associate Professor of Criminology, Law & Society, Vice Chair of the Department of Psychological Science at the University of California, Irvine

William Crozier – Research Director of the Wilson Center for Science and Justice

The presenters have provided a copy of the paper discussed.

Presentation Description:

We will describe two recent experiments.  In the first, we conducted two studies whether knowledge of an expert’s performance on blind proficiency testing affects trust in the expert witness, the evidence (fingerprint or bitemark), and verdicts.  We also examined whether cross-examination affected these outcomes.  As labs consider adopting blind proficiency testing programs, we wanted to better understand how information about those programs impacts jurors.  Our results support the view that additional blind proficiency testing programs, in addition to their quality control benefits, do not prejudice jurors.
Second, firearms experts traditionally have testified that a weapon leaves “unique” toolmarks, so bullets or cartridge casings can be visually examined and conclusively matched to a particular firearm. Recently, due to scientific critiques, Department of Justice policy, and judges’ rulings, firearms experts have tempered their conclusions. In two experiments, we tested whether this ostensibly more cautious language has its intended effect on jurors (Experiment 1), and whether cross-examination impacts jurors’ perception of firearm testimony (Experiment 2). We found that apart from the most limited language (“cannot exclude the defendant’s gun”), judicial intervention to limit firearms conclusion language is not likely to produce its intended effect. Moreover, cross-examination does not appear to affect perceptions or individual juror verdicts.


In recognition of a $5 million dollar grant from the Wilson Foundation, CSAFE partner institution Duke University renamed its Center for Science and Justice the Wilson Center for Science and Justice. Funds from the grant will expand the center’s work in three key areas: accuracy of evidence in criminal cases, the role of equity in criminal outcomes, and the mental and behavioral health treatment needs of people in the justice system. 

CSAFE’s own Co-Director, Brandon Garrett, the L. Neil Williams Jr. Professor of Law and Faculty Director of the center, aims for Duke Law School to build a long-term presence as a national leader in reforming the US criminal justice system. The Center, originally launched in September 2019, plans to encourage and instruct students and faculty on how to bolster legal and scientific data-driven research.  

“Bringing law and science together to prevent injustice has been my life’s work, since I was a young lawyer, and now, in my work with the new Wilson Center for Science and Justice at Duke,” said Professor Garrett. 

The Wilson Center champions the integration of students, faculty, and staff across multiple disciplines, gathering their expertise in law, public policy, medicine, the arts, and sciences, to create a unique lens for criminal justice research. The philosophy of interdisciplinary collaboration driving impactful research, policy, and teaching is what forms the foundation of our educational initiatives at CSAFE.

Strengthening research in the prevention of wrongful convictions, the examination of how jurors evaluate forensic evidence, and the accuracy of evidence in court are primary objectives of the Wilson Center — all of which cannot be achieved without the practice of scientifically valid methods. At its core, CSAFE is committed to the application of verified statistical and scientific techniques to ensure the accuracy of forensic analysis and interpretation and to uphold the fair administration of justice.

With more than just a strong alignment of legal and scientific ideology, CSAFE’s partnership with the Wilson Center for Science and Justice will strengthen the field of forensic science and remedy structural inequalities ingrained in the justice system.

Click here to learn more about CSAFE’s commitment to statistical and scientific data-driven research. 

Closed Source Forensic Software: Confronting the Evidence?

There is a persistent underlying flaw in the criminal justice system, stemming from unvalidated forensic science cloaked in intellectual property. Not only does this pose a risk when forensic evidence is a key factor in criminal convictions, but it also reveals how confidential forensic technology could violate defendants’ constitutional rights. 

Forensic analysis software, used to generate evidence in criminal trial proceedings, frequently contains closed source code. Such proprietary software prevents the scientific community, the public, juries, attorneys, and defendants from accessing the fundamental methods — or potential errors therein — that can ultimately influence verdicts. This creates a pathway for individuals to be wrongly convicted as a result of jurors being swayed by flawed evidence disguised as good science. 

An excellent example is the case of United States v. Ellis, in which DNA was the key evidence used against the defendant accused of illegal firearm possession. The police forensic lab found the DNA analysis inconclusive, prompting further analysis by third-party-owned software. With multiple hypotheses and test variations run on the sample, the prosecution relied on the result of one particular analysis based on the assumption that the defendant was one of four possible contributors to the DNA sample. 

When Mr. Ellis’ attorney requested access to the source code, “…the government refused to disclose it, arguing that the information is protected by trade secrets.” 

In response, the Electronic Frontier Foundation (EFF) and American Civil Liberties Union of Pennsylvania filed an amicus with the United States District Court of the Western District of Pennsylvania, outlining the inconsistency between closed source code, the defendants’ Sixth Amendment rights, and the right of the public to oversee the criminal trial. 

Source code, and other aspects of forensic software programs used in a criminal prosecution, must be disclosed in order to ensure that innocent people do not end up behind bars,” said the EFF. “Or worse — on death row.”

While it is understandable that developers of forensic software wish to protect their intellectual property, it raises a fundamental question: should IP be protected at the expense of civil rights? To protect the innocent, maintain public oversight, and ensure the advancement of forensic science practices, the curtain must be pulled back on protected methodologies. Arguably, the benefits of doing so would lead to fairer trials and greater trust in the scientific tools utilized within the criminal justice system.

Click here to learn more about CSAFE’s commitment to open source tools.

CSAFE 2020 All Hands Meeting

The 2020 All Hands Meeting was held May 12 and 13, 2020 and served as the closing to the last 5 years of CSAFE research and focused on kicking off new initiatives for the next phase of the center, CSAFE 2.0.

CSAFE brought together researchers, forensic science partners and interested community members to highlight the organization’s achievements, identify areas for collaboration, and discuss goals for the future. It was an opportunity to connect with innovative experts in statistical foundations, pattern and digital evidence, and training and education to learn from each other and discuss potential collaborations.

The recordings of the research updates are available below. All videos along with other CSAFE webinars can be viewed on the CSAFE YouTube.

Opening and Kick-off for CSAFE 2.0

Dr. Alicia Carriquiry, CSAFE, Iowa State University and Robert Ramotowski, National Institute of Standards and Technology

Session 1: Firearms and Toolmark Analysis

Dr. Heike Hofmann, CSAFE, Iowa State University 

Session 2: Footwear Impression Analysis

Dr. Charless Fowlkes, CSAFE, University of California, Irvine

Session 3: Bloodstain Pattern Analysis

Dr. Hal Stern, CSAFE, University of California, Irvine

Session 4: Handwriting Analysis

Dr. Alicia Carriquiry, CSAFE, Iowa State University

Keynote Presentation

Lynn Garcia, General Counsel, Texas Forensic Science Commission

Session 5: Latent Print Analysis

Dr. Karen Kafadar, CSAFE, University of Virginia

Session 6: Digital Evidence

Dr. Padhraic Smyth, CSAFE, University of California, Irvine

Session 7: Statistics

Dr. Danica Ommen, CSAFE, Iowa State University 

Session 8: Implementation and Practice

Brandon Garrett, CSAFE, Duke University School of Law 

Session 9: Education and Training

Dr. Robin Mejia, CSAFE, Carnegie Mellon University 


Implementing Blind Proficiency Testing

This CSAFE Center Wide webinar was presented on July 18, 2019 by Dr. Robin Mejia, CSAFE researcher at Carnegie Mellon University. Dr. Mejia provided presentation slides.

Presentation Description:

Blind proficiency testing is a norm or requirement in many scientific fields. However, forensic laboratories primarily rely on open proficiency tests from vendors such as Collaborative Testing Services, Inc. or Forensic Assurance. In open proficiency tests, examiners know they are being tested, and the test targets a specific step in the evidence handling and analysis pipeline.  In blind proficiency tests, examiners are unaware they are being tested and, as the sample moves through the laboratory’s evidence handling and management pipeline, it can provide data on the entire process from evidence submission to analyst report.  Studies in other fields have shown that laboratories often perform differently on open and blind proficiency tests. A growing number of voices within the community of forensic quality managers and some laboratory directors have expressed interest in implementing blind testing in addition to open proficiency tests.  However, implementing blind proficiency testing is logistically challenging, and takes both time and money, neither of which tend to be in surplus at forensic laboratories. This webinar will report on the CSAFE 2018 Blinding Workshop, highlighting experiences, issues, and best practices for laboratories implementing blinding.


Identifying Digital Evidence from Android Devices via Static and Dynamic Analysis

This CSAFE Center Wide webinar was presented on June 25, 2019 by Dr. Yong Guan, CSAFE researcher at Iowa State University.

Presentation Description:

The over 50 app stores across the world provides mobile phone users with access to 8 million apps, each with the potential to house important forensic evidence. It is not possible for digital forensic practitioners to develop sufficient expert knowledge about every single app on the market. As a result, this often prevents timely and reliable discovery of forensic evidence, leading to backlogs in most crime laboratories. Researchers will discuss EviHunter, a new forensic Android app analysis toolset, and with it, build the likely largest Android App Forensic Evidence Database, to assist crime investigators to solve these issues.


How Jurors Evaluate Fingerprint Evidence

This CSAFE Center Wide webinar was presented on April 2, 2019 by Brandon Garrett, CSAFE researcher and the L. Neil Williams Professor of Law at Duke University. Brandon Garrett has provided presentation slides.

If you should require a certificate for attending this webinar, please email Marc Peterson at

Presentation Description:

The way jurors examine the reliability of forensic evidence, such as fingerprints, during trial proceedings remains an important question in forensic science. Recent studies have explored new ways to convey information to potential jurors. This webinar will examine how potential jurors respond to these novel methods and explore ways to better educate jurors on the strength and limitations of forensic conclusions.

Similarity of Two-Dimensional Images: An application to the forensic comparison of shoe outsole impressions

This CSAFE Center Wide webinar was presented on March 11, 2019 by Dr. Soyoung Park, CSAFE Post Doctoral researcher at Iowa State University. Dr. Park has provided presentation slides.


Presentation Description:

Shoe outsole prints are often found in crime scenes.  If a suspect is apprehended and her shoes are potential sources of the prints in the crime scene, how might a forensic scientist go about quantifying the degree of similarity between the two?  As is the case for most other types of pattern evidence, quantifying the similarity between two impressions is challenging.  The traditional statistical modeling approach is not appropriate in these cases, so we turn to learning algorithms as a potential alternative. In this talk, we discuss a method that compares two dimensional images, one of a latent crime scene print, and one of a known shoe, and produces a score that quantifies the degree of similarity between the two.   The method we have developed is promising, because it appears to correctly determine with high probability whether two images have a common or a different source, at least for the shoes on which we have experimented.


Covering the Basic Concepts Surrounding the Weight and Strength of Evidence

This CSAFE Center Wide webinar was presented on January 7, 2019 by Dr. Danica Ommen, CSAFE researcher and Assistant Professor at Iowa State University. Dr. Ommen has provided presentation slides for Part 1 and Part 2 and references.


Presentation Description: 

In this two-part presentation, we will focus on aspects of the forensic identification of source problems where the main question of interest is determining the origin of evidence with unknown source.  In order to solve this problem, we need to determine the value of the evidence with respect to two competing propositions for its origin by computing some type of “likelihood ratio.”  After we get this value of evidence, the idea is that it can be used to help someone make a decision.  In the case of a criminal trial, the decision would be regarding the guilt or innocence of the defendant.  However, there are many different ideas about what the “likelihood ratio” should look like and how to compute its value, especially in the face of uncertainty.  Often, we are uncertain about the statistical models we’ve chosen to describe the evidence.  In this presentation, we will discuss the basic definitions, as well as various computational strategies, for both the weight and the value of evidence.  In addition, we will review and discuss recent controversies surrounding the value of evidence.


Part 1


Part 2

Research and Crime Scene Reconstruction: What should it look like?

This CSAFE Center Wide webinar was presented on December 13, 2018 by Professor Keith Inman, CSAFE colleague and Associate Professor at California State University East Bay. Professor Inman has provided presentation slides.


Presentation Description: 

Every stake holder claims dominion over the reconstruction of a violent event (detectives, attorneys, scientists, trier-of-fact), yet most have nothing but common (non)-sense and parochial experience to guide their efforts. What can and should the scientist contribute to an understanding of the aftermath of a violent encounter? What constitutes a ‘scientific’ inquiry into such an occurrence?

Most research conducted in this area focuses on specific evidence types typically encountered at crime scenes, and research in one evidence type is isolated from other evidence types. It is almost always conducted by forensic scientists, which is reasonable and natural. This talk will explore the limitations of such an approach, and suggest asking and answering key reconstruction questions from a holistic perspective, incorporating the expertise of research and work in several other fields. Such collaborations have the potential to advance our fundamental knowledge of violent events, and guide our investigation and reconstruction of crime scenes.