A comment on the PCAST report: skip the “match”/“non-match” stage

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

*Corresponding author for this work

Research output: Contribution to journalLetter, comment/opinion or interviewpeer-review


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.

Original languageEnglish
Pages (from-to)e7-e9
Number of pages3
JournalForensic Science International
Early online date26 Oct 2016
Publication statusPublished - 1 Mar 2017

Bibliographical note

© 2016, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/


  • false alarm
  • forensic statistics
  • likelihood ratio
  • match/non-match
  • PCAST report
  • sensitivity to pressure and temperature


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