MODULE 7: Uncertainty and Limitations of Probabilistic Genotyping Systems

MODULE 7: Uncertainty and Limitations of Probabilistic Genotyping Systems

← Back to Series 

This module originally occurred on June 26, 2019
Duration: 4 hours


Module 7: Uncertainty and Limitations of Probabilistic Genotyping Systems

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. Probabilistic reasoning provides a means to characterize these results, given the unknown information in forensic evidence, the stochastic environment, and sources of variability. Instructors in Module 7 will explore strategies of interpretation and decision making in light of these and other variables, such as the uncertain number of contributors, and will share research on the impact of these variables on the likelihood ratio.

Additionally, courts are becoming increasingly interested not just in “whose DNA is this?” but “how did the DNA get there?” Therefore, the instructors will revisit topics introduced earlier in the series to dive deeper into the relevance of a DNA profile, given today’s advanced detection sensitivity and the potential for DNA transfer, as well as activity level reporting and the hierarchy of propositions.

Detailed Learning Objectives

  1. Describe sources of uncertainty in mixture interpretation and their influence on the likelihood ratio
  2. Devise a strategy to address contributor number assignment/re-assignment
  3. Address questions regarding the potential for DNA to be transferred through contact and persist on evidence
  4. Be aware of developments that assist the courts in considering activity level propositions


  • Amke Caliebe | University of Kiel, Kiel, Germany
  • Zane Kerr | Institute on Environmental Science and Research, Auckland, New Zealand
  • Klaas Slooten | Netherlands Forensic Institute & Vrije University, Amsterdam, The Netherlands
  • Bianca Szkuta | Victoria Police Forensic Services Department & Deakin University, Geelong, Australia

Funding for this Forensic Technology Center of Excellence webinar has been provided by the National Institute of Justice, Office of Justice Programs, U.S. Department of Justice.

The opinions, findings, and conclusions or recommendations expressed in this webinar are those of the presenter(s) and do not necessarily reflect those of the U.S. Department of Justice.

Contact us at with any questions and subscribe to our newsletter for notifications.

Related Content

Data Exchange Practices of Medicolegal Death Investigation

Date December 2022 Overview The National Institute of Justice (NIJ)-in partnership with its Forensic Technology Center of Excellence (FTCOE) at RTI International and the National Center for Health Statistics, Centers for Disease Control and Prevention (CDC)-convened a virtual Medicolegal Death…

The Sentinel Role of Forensic Toxicology Laboratories to Identify and Act Upon Diverse Drug Threats by Addressing Toxicology and Economic Demands

Publication Forensic Science International: Synergy, September, 2022 Authors Jeri D. Ropero Miller | RTI International Lawrance D. Mullen | RTI International Paul J. Speaker | West Virginia University Introduction The societal costs from substance abuse are extensive and include treatment…