A comprehensive study into false positive rates for ‘other’ biological samples using common presumptive testing methods

[Display omitted] •A range of commonly used body fluid identification tests for blood, semen and saliva were assessed.•Samples tested were blood, semen, saliva, urine, sweat, vaginal material, faeces and breast milk.•False positive rates were determined for inclusion in reporting frameworks. The ide...

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Bibliographic Details
Published in:Science & justice 2023-05, Vol.63 (3), p.414-420
Main Authors: Stroud, Angela, Gamblin, Amelia, Birchall, Penny, Harbison, SallyAnn, Opperman, Stephanie
Format: Article
Language:English
Subjects:
Body fluid identification
Body Fluids
False positive results
Female
Forensic Medicine
Forensic science
Forensic Sciences
Humans
Saliva - chemistry
Semen
Specificity testing
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Summary:[Display omitted] •A range of commonly used body fluid identification tests for blood, semen and saliva were assessed.•Samples tested were blood, semen, saliva, urine, sweat, vaginal material, faeces and breast milk.•False positive rates were determined for inclusion in reporting frameworks. The identification of biological fluids or materials in forensic samples is a key requirement in forensic science that relies on chemical and biological based tests, most of which exhibit false positivity. When reporting results from such tests, Forensic Scientists use words such as probable, possible, and likely, without always being able to provide robust support for these conclusions. In collating information about false positive rates for a number of these tests, we found limited research into the cross reactions observed from ‘other’ biological samples in commonly encountered case sample stains. By ‘other’ we mean biological fluids or materials that are not the primary target of the presumptive test being used. Here we carry out a specificity study to fill gaps in the literature for a number of the presumptive chemical, biological and immunochromatographic tests used to presumptively screen for blood, semen and saliva. The tests selected for this study are the widely used tests: Luminol, TMB/Combur3 Test® E, Kastle-Meyer (KM), RSID™ - Blood, ABAcard® HemaTrace®, Acid Phosphatase (AP), ABAcard® p30, RSID™ - Semen, Phadebas® ‘Tube’ Test, Phadebas® ‘Press’ Test, and RSID™ - Saliva tests. Specificity for each of these was tested in known samples, from volunteers, of blood, semen, saliva, urine, sweat, vaginal material, faeces and breast milk, and then false positive rates were determined.
ISSN:1355-0306
1876-4452
DOI:10.1016/j.scijus.2023.04.006