mixSTR Mixture Tool


Participants: David L. Duewer


Project Timeframe: March 2005 to June 2005


Purpose: A number of Microsoft Excel-based tools have been developed at NIST to aid internal research projects funded by the National Institute of Justice. Some of these software tools may prove useful for application in forensic casework. The mixSTR tool, developed in collaboration with the Palm Beach Sheriff’s Office (PBSO), helps identify reference profiles in sets of mixed-source samples.  Given allele lists for one or more evidential samples and all relevant suspect and control reference profiles, the MixSTR system provides detailed lists of the match and miss-match alleles among all samples and profiles.  Sorted summaries of the percent of included alleles and loci for all comparisons are also provided.  This tool is intended for use by all forensic scientists working with mixed-source samples.


Progress: The program was completed within a few days of the request by PBSO. Comparisons are made between suspect and evidence (S/E) alleles, suspect and suspect (S/S) alleles (to look for potential close relatives), evidence and other evidence (E/E) sample(s) alleles (to see how various evidentiary samples compare to one another), and controls to evidence (C/E) and controls to suspect (C/S) alleles (as a quality control contamination check). The program can be downloaded from NIST STRBase web site: http://www.cstl.nist.gov/div831/strbase/software.htm and runs with Microsoft Excel.


Publications or Presentations Resulting From This Project:

David Duewer and John Butler demonstration and posters at NIJ DNA Grantees meeting (Washington, D.C.), June 28, 2005, "Multiplex_QA: An Exploratory Quality Assessment Tool for STR Multiplex Assays" [.pdf] and "New Tools to Aid Work with STR Profile Mixtures: mixSTR and Virtual MixtureMaker" [.pdf]


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Last updated: 06/20/2007


Disclaimer: This project was supported by National Institute of Justice Grant Number 2003-IJ-R-029, which is an interagency agreement between NIJ and the NIST Office of Law Enforcement Standards, awarded by the National Institute of Justice, Office of Justice Programs, US Department of Justice. Points of view in this document are those of the authors and do not necessarily represent the official position or policies of the US Department of Justice. Certain commercial equipment, instruments and materials are identified in order to specify experimental procedures as completely as possible.  In no case does such identification imply a recommendation or endorsement by the National Institute of Standards and Technology nor does it imply that any of the materials, instruments or equipment identified are necessarily the best available for the purpose.