A comment on the PCAST report: Skip the "match"/"non-match" stage

Published

March 1, 2017

Author(s)

Geoffrey S. Morrison, David H. Kaye, David J. Balding, Duncan Taylor, Phillip Dawid, Colin Aitken, Simone N. Gittelson, Grzegorz Zadora, Bernard Robertson, Sheila Willis, Susan Pope, Martin Neil, Kristy A. Martire, Amanda Hepler, Richard Gill, Allan Jamieson, Jacob de Zoete, R. B. Ostrum, Amke Caliebe

Abstract

This letter comments on the report "Forensic science in criminal courts: Ensuring scientific validity of feature-comparison methods" recently released by the President's Council of Advisors on Science and Technology (PCAST). The report advocates a procedure for evaluation of forensic evidence that is a two-stage procedure in which the first stage is "match"/"non-match" and the second stage is empirical assessment of sensitivity (correct acceptance) and false alarm (false acceptance) rates. Almost always, quantitative data from feature-comparison methods are continuously-valued and have within-source variability. We explain why a two-stage procedure is not appropriate for this type of data, and recommend use of statistical procedures which are appropriate.

Citation

Forensic Science International

Pub Type

Journals

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Keywords

PCAST report, forensic statistics, match/non-match, sensitivity, false alarm, likelihood ratio.

Citation

Morrison, G. , Kaye, D. , Balding, D. , Taylor, D. , Dawid, P. , Aitken, C. , Gittelson, S. , Zadora, G. , Robertson, B. , Willis, S. , Pope, S. , Neil, M. , Martire, K. , Hepler, A. , Gill, R. , Jamieson, A. , de Zoete, J. , Ostrum, R. and Caliebe, A. (2017), A comment on the PCAST report: Skip the “match”/“non-match” stage, Forensic Science International, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=922201 (Accessed October 16, 2025)