Inferring the number of contributors to mixed DNA samples
Evidence samples containing DNA from two or more people can be difficult to interpret. Even ascertaining the number of contributors can be challenging. Underestimating the number of contributors can have important bearing on forensic casework and is surprisingly common -- especially if analysts are allowed to disregard seemingly inconsistent data from some loci.
RecordedSep 23 200846 mins
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Jack Ballantyne, Assoc Director; National Center For Forensic Science
The serology-based methods routinely used in forensic casework for the identification of biological fluids have varying and often limited degrees of sensitivity and specificity. A novel strategy for the identification of the body fluid origin of dried forensic biological material (blood, semen, saliva, vaginal secretions and menstrual blood) involves expression profiling of body fluid specific messenger and small RNAs (mRNA and miRNA). RNA analysis may permit not only a molecular-based approach with a greater specificity than that of conventional methodologies for the identification of forensically relevant biological fluids, but may also provide strategies particularly suited for the analysis of environmentally impacted or degraded samples frequently encountered in forensic casework. This presentation will describe highly specific RNA methods for body fluid identification that exhibit promise for forensic casework analysis.
Amarjit Chahal, Senior Director; Warnex Pro-DNA Services, Inc.
The analysis of regular STR DNA has become the “gold standard” of identification in forensic casework. There are numerous cases though where biological evidence exists but regular DNA testing can’t provide probative evidence or insufficient nuclear DNA was obtained. This presentation will describe casework scenarios where miniSTR, Y-STR and/or mtDNA can provide probative evidence.
Brian Zubel: Attorney at Law and Forensic Science Legal Consultant
In February 2009, the National Research Council of the National Academies released its report entitled Strengthening Forensic Science in the United States: A Path Forward. The substantive findings underscore that many traditional forensic disciplines are in scientific crisis, having never been the subject of rigorous validation. This presentation outlines the major findings of the Report, and the impact it will have on the roles of prosecutors, defense attorneys and judges in the rapidly evolving scientific/legal landscape.
Diana Botluk; Director of Research at NCSTL at Stetson Uni. College of Law
This program will explore information and research resources in forensic science, focusing primarily on the resources available from the National Clearinghouse for Science, Technology and the Law at Stetson University College of Law. It will demonstrate features of ncstl.org, such as the free research database, Cold Case Toolkit, Education Center, and other online resources designed to keep you updated with the latest scientific evidence information.
Dr. Thomas R. Bellinger, President of NecroSearch International
This presentation will provide an introduction to NecroSearch International, a non-profit, multi-disciplinary organization dedicated to the location of clandestine graves and evidence. A brief history of NecroSearch will be presented along with a description of the organization's mission (research, training, and investigation) and case acceptance protocol. Several of the organization's expertise categories will be discussed along with a description of NecroSearch's investigative process. The presentation will conclude with a case example.
Amarjit Chahal, Laboratory Director & General Manager at Molecular World Inc
Part of the nuclear DNA that is paternally inherited or passed down from father to son is found on the Y chromosome. Similar to mitochondrial DNA, Y-chromosome testing can be used to distinguish between individuals with different paternal lineages. Short tandem repeats (STR) on Y chromosome are called Y-STRs. Y-STR testing is identical to analyses of nuclear autosomal STR loci. Testing for this type of DNA is particularly useful when mixtures of male DNA (a minor male contributor) and female DNA (predominant female contributor) are suspected or only distant paternal relatives are available for comparisons. The presentation will introduce audience to Y-STR testing with a particular focus on the probative value of Y-STR DNA test reports.
Brian Zubel: Attorney at Law and Forensic Science Legal Consultant
The presentation will begin with a discussion of the effective presentation of DNA evidence in court, including admissibility standards, foundational issues and the limits of argument. Current-generation legal and scientific challenges to DNA will be explored through the review of several recent cases.
Dick Warrington: Crime Scene instructor/Consultant,Lynn Peavey Company
This presentation will show the attendees three methods of lifting developed latent fingerprints off textured surfaces. The three methods that we will talk about are Diff-Lift tape, Mikrosil, and AccuTrans. By using one of these methods demonstrated you’ll be able to lift processed latent fingerprints off a car dash, refrigerators, bank countertops, computers, house siding and a golf ball, just to name a few.
Jack Ballantyne, Assoc Director (Research);National Center For Forensic Science
The development of powerful and robust DNA typing strategies has made it is possible to ascertain with a high degree of certainty whether a biological stain found at a crime scene originated from a particular individual. However, the possibility of obtaining additional information from biological stains exists. For example, the ability to determine the relative time since deposition (TSD) of biological stains could provide law enforcement investigators with novel probative evidence by establishing an approximation of the time of commission of criminal offenses. However, no reliable TSD methods are available at present. We have developed a novel strategy for the determination of the time since deposition of dried bloodstains using spectrophotometric analysis of hemoglobin. An examination of the Soret band in aged bloodstains has revealed a previously unidentified hypsochromic shift (shift to shorter wavelength). The extent of this shift permits a distinction to be made between stains that were deposited minutes, hours, days and months prior to analysis. The effects of temperature and humidity have also been evaluated.
Roger Koppl, Director of the Institute for Forensic Science Administration
The current institutional structure of police forensics gives each lab a monopoly in the analysis of the police evidence it receives.
Forensic scientists have inadequate incentives to produce reliable analyses of police evidence. We should have "competitive self regulation" for police forensics. Each jurisdiction would have several competing forensic labs. Sometimes, evidence would be divided and sent to three separate labs. Chance would determine which labs would receive evidence to analyze. Competitive self regulation improves forensics by creating incentives for error prevention, detection and correction. Surprisingly, it would also reduce the costs of running the criminal justice system.
D. Michael Risinger, John J. Gibbons Professor of Law, Seton Hall University
Domain Irrelevant Information as an Infectious Disease in Forensic Science Practice
In this presentation, Professor Risinger discusses the distorting effects of case information irrelevant to the exercise of one's expertise on the results interpretive processes in forensic science, analogizing such information to an infectious disease. The empirical record bearing on these issues is examined, particularly those empirical results specifically relevant to forensic science practice.
This presentation helps lawyers view complex DNA cases in a new light, while comparing the Duke Lacrosse Case to others. Attorneys do not have to concede when they hear the words "match" or "defendant cannot be excluded". Instead, they should remember that besides standing for deoxyribonucleic acid, DNA also stands for DO NOT ACCEPT at face value. This article looks at the DNA evidence in the Duke Lacrosse case and compares the evidence in that case with DNA evidence in other cases.
This presentation offers practical tips on reviewing complex data generated in DNA cases, discusses the importance of the proper collection and preservation of DNA evidence, discusses the likelihood and ways DNA evidence is subject to contamination, and outlines specific ways to cross-examine DNA experts.
PCR-based DNA tests have greatly improve the capabilities of forensic laboratories. The great successes of these tests have inevitably led to efforts to characterize smaller and smaller amounts of material. As the quantity of DNA template associated with a DNA profile test decreases, the likelihood that the results of the test will be compromised by stochastic effects increases. Questions about the significance of results in such circumstances will be addressed
-- particularly as they pertain to a prominent acquittal in the United Kingdom where low copy number test results played a central role in the prosecution's case.
King Brown and M. Dawn Watkins of the Palm Beach Police Department
The IR-UV camera is a new breakthrough in the forensic field that allows us to drop the background color say a black shirt and show the blood stain patterns, thus allowing for photography, collection testing interpretation of the pattern.
Dr. Amarjit Chahal, Laboratory Director & Technical Leader, Molecular World Inc
Increasing the probative value of degraded or limited DNA evidence by combining two or more DNA technologies: Combining DNA data from all technologies (for example partial nuclear DNA profile, Y-STR profile and mitochondrial DNA profile in case of degraded samples) to increase the probative value of final DNA test report.
Roger Koppl, Institute for Forensic Science Administration Fairleigh Dickinson
The organization of forensic science creates inappropriate biases that will sometimes skew results from the truth. These biases exist even when forensic scientists are perfectly rational and untouched by the sort of psychological infirmities some researchers have emphasized.
Because perfectly rational actors are Bayesian updaters, we may use the term "Bayesian bias" to identify this organizational problem in forensics.