Forensic and Investigative Sciences

Throughout the Probabilistic Genotyping of Evidentiary DNA Typing Results virtual workshop series, we have reviewed aspects of DNA mixture interpretation and have seen that probabilistic genotyping (PG) software can serve as a tool to assist the DNA Examiner in identifying possible genotype sets within a mixture and then calculating a likelihood ratio (LR). Approaches to modeling were shared by the developers of different PG software programs, followed by examples of internal validation studies and results.

By combining the data in ODMAP with collaborative partnerships which span different disciplines, localities can develop and deploy a real-time plan to reduce both fatal and non-fatal overdoses.

This webinar was presented by the NIJ Forensic Technology Center of Excellence on July 16, 2019.

Practitioners from across the criminal justice system speak to the importance of cold case units and the impact they can have.

Practitioners from across the criminal justice system speak to the impact of NIJ's Solving Cold Cases with DNA grant program.

Has a person of interest contributed DNA to a mixture obtained from evidence? Is that DNA associated with a crime? Both are questions that cannot be answered with absolute certainty. This module of the Probabilistic Genotyping of Evidentiary DNA Typing Results workshop series addresses the uncertainty and limitations of probabilistic genotyping systems that are used to calculate likelihood ratios and infer genotype sets from DNA typing results.

Locating and notifying the next of kin is an important part of medicolegal death investigation. This presentation provided examples of resources at the scene and online to assist medicolegal death investigators (MDIs) with identifying the decedent’s next of kin. Some of these resources include talking to witnesses, searching cell phone information, social media accounts, public records, and criminal databases. Additionally, Namus was discussed as a resource if a next of kin cannot be identified. 

Biological modeling, statistical theory, and the computer processing of probabilistic genotyping systems are based on long- standing principles, yet their usage in U.S. courts has been limited to the past few years. This module of the Probabilistic Genotyping of Evidentiary DNA Typing Results web series addresses topics relevant to the admissibility of probabilistic genotyping results and the presentation of results in criminal proceedings. Various decisions related to probabilistic genotyping will be summarized from a legal perspective.

Historically, the predominant means of assigning statistical weight to many DNA mixtures in the U.S. has been the combined probability of inclusion, or CPI. Accordingly, many forensic DNA analysts, as well as attorneys and judges, are well-versed in the CPI as a match probability. In the fifth module of this workshop series devoted to probabilistic genotyping, the presenters will help DNA analysts and legal professionals understand degrees of statistical weight and properly communicate likelihood ratios and their meaning.

The Scientific Working Group on DNA Analysis Methods (SWGDAM) and other bodies have published guidelines that specify empirical studies to be performed to assess reliability, identify limitations and develop suitable usage conditions for probabilistic genotyping systems.