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DNA Analyst Training on Mixture Interpretation

The National Institute of Standards and Technology (NIST)

hosted a free one-day workshop on interpreting forensic DNA mixtures in casework. This workshop was webcast live to maximize participation by forensic DNA analysts.  

Link to Archived Webcast

DNA Mixture Interpretation Webcast Agenda

EPG Maker Software (See bottom of software programs or information section)

Printable Workshop Slides (Full Workshop) – 77 pages with 6 slides per page

Full Screen Slides by Presentation

Printable Workshop Examples

Link to Workshop Poll Questions

Responses to 20 Poll Questions During Workshop & Webcast

Latest Conference Announcements


DNA mixtures can be difficult to interpret and represent one of the biggest challenges faced by forensic laboratories today. With the success of DNA in the criminal justice system giving rise to expanded case acceptance policies, many DNA analysts are coping with complex mixtures arising from three or more contributors and/or low-level DNA samples. A free eight-hour internet-based training workshop geared towards the needs of forensic DNA analysts was broadcast from NIST on Friday, April 12, 2013. The training materials were similar to what was presented at the 2012 International Symposium on Human Identification (see The mixture examples that were worked as part of the training were available for download prior to the webcast to enable participants to examine them using their own laboratory protocols.

Presenters for this webcast included John Butler and Mike Coble from the NIST Applied Genetics Group as well as Robin Cotton (Boston University), Charlotte Word (consultant), and Bruce Heidebrecht (Maryland State Police). Topics covered included why mixtures are difficult, what approaches are being taken around the world to cope with complex mixtures, how validation studies should guide mixture interpretation protocols, and what statistical approaches are appropriate to use in different situations. Multiple examples were worked to illustrate the fundamental principles of mixture interpretation.

Learning Outcomes:

  1. Explore how the analytical threshold and stochastic threshold affect data analysis, interpretation, conclusions and statistical calculations in mixed DNA profiles.
  2. Examine approaches for establishing one or more analytical thresholds and stochastic thresholds for casework.
  3. Enhance knowledge of mixture interpretation and presentation of results, conclusions and opinions.


On-site attendees were DNA analysts, technical reviewers, or technical leaders performing and interpreting validation studies and/or interpreting and reviewing STR data. 

Webcast Minimum Technical Requirements:

The Webcast streamed in medium bandwidth (350kbs), so viewers needed to have a constant connection during the webcast.

Hardware and operating system configurations

  • Windows XP (Internet Explorer or Firefox)
  • Windows Vista (Interent Explorer or Firefox)
  • Windows 7 (Internet Explorer or Firefox)
  • Apple Mac OS 10.5x (Firefox or Safari)
  • Ubuntu Linux (Firefox only)

Media players

In order to access the event, you must have, at minimum, Flash Player 10.x installed on your computer.
Please visit: to download the Flash Player.

Internet browsers

In order to access the event, you must have either Microsoft Internet Explorer 6.0+ or Mozilla Firefox 3+ browser for Windows operating systems. For accessing events via Mac operating systems you must have Mozilla Firefox 3+ or Safari 4.x.

Certificates Of Completion:

All onsite attendees will receive a certificate of completion. Individuals viewing the live webcast who want to receive a certificate of completion must register using the registration link "VIEW WEBCAST ONLY" AND after completion of the live webcast, the Technical Leader of the webcast viewer's DNA laboratory must email john.jones [at] (john[dot]jones[at]nist[dot]gov) with a list of all laboratory participants who viewed the live webcast and require a certificate. The list provided by the Technical Leader will be cross-referenced against the "VIEW WEBCAST ONLY" registration list, and then appropriate certificates will be generated. The certificates of completion will be emailed to the Technical Leader to distribute to the individual viewers.

Agencies that choose to use one computer to access the webcast and have multiple individuals watch the webcast from a single computer are invited to do so. If those individuals watching the webcast require a certification of completion, please follow the instructions above to properly register each individual. 

This webcast can be considered continuing education via internet delivery as defined under QAS Standard below. Please consult with your laboratory Technical Leader to review and approve this training for continuing education.

Relevant Portion of Quality Assurance Standards for Forensic DNA Laboratories: Continuing education: The technical leader, casework CODIS administrator, and analyst(s) shall stay abreast of developments within the field of DNA typing by attending seminars, courses, professional meetings or documented training sessions/classes in relevant subject areas at least once each calendar year. A minimum of eight cumulative hours of continuing education are required annually and shall be documented. If the continuing education is conducted externally, the laboratory shall maintain documentation of attendance through a mechanism such as certificates, program agenda/syllabus, or travel documentation. Attendance at a regional, national or international conference shall be deemed to provide a minimum of 8 hours of continuing education. Programs based on multimedia or internet delivery shall be subject to the approval of the technical leader. Participation in such programs shall be formally recorded and its completion shall be submitted to the technical leader for review and approval.  The documentation shall include the time required to complete the program.

All foreign national visitors who do not have permanent resident status and who wish to register for the above meeting must supply additional information. Failure to provide this information prior to arrival will result, at a minimum, in significant delays (up to 24 hours) in entering the facility. Authority to gather this information is derived from United States Department of Commerce Department Administrative Order (DAO) number 207-12. When registration is open, the required NIST-1260 form will be available as well.

Created December 17, 2012, Updated May 13, 2016