The Art in the Science of DNA: A Layperson's Guide to the Subjectivity Inherent in Forensic DNA Typing

24 Pages Posted: 3 Feb 2011

See all articles by Erin Murphy

Erin Murphy

New York University School of Law

Date Written: February 2, 2008


DNA typing is typically held out as the pinnacle of "good" forensic evidence, in that it exemplifies the kind of scientific rigor that first-generation techniques lack. And, without question, this praise is well-deserved. DNA typing represents a marked advance beyond the shamanistic "sciences" of the first generation. Yet the seeming corollary - that DNA typing is therefore an exercise in purely objective, indisputable science - does not hold true. This is not to suggest that DNA has no basis in objective science, or even that it is as subjective as other forensic techniques; comparing most first-generation methods to DNA typing is like comparing astrology to neuroscience. Nevertheless, not unlike neuroscience, the fact that DNA typing is scientifically grounded does not mean that there are not plenty of things that we still do not understand about it, and plenty of instances in which the best conclusions we can draw are nonetheless tentative ones. To be clear, I am not saying that DNA typing done poorly entails an exercise of subjective judgment. Rather, DNA typing - done perfectly and precisely according to protocol - still often entails making discretionary calls and choices. But just because DNA typing is not wholly objective does not mean that it is wholly indeterminate - it simply means that it may be more like meteorology than mathematics. This Article explains, in what I hope is accessible language, some of the the subjective discretion involved in forensic DNA typing.

Keywords: DNA, subjectivity, forensic typing, discretion, guide

JEL Classification: K14

Suggested Citation

Murphy, Erin Elizabeth, The Art in the Science of DNA: A Layperson's Guide to the Subjectivity Inherent in Forensic DNA Typing (February 2, 2008). Emory Law Journal, Vol. 58, No. 489, 2008, Available at SSRN:

Erin Elizabeth Murphy (Contact Author)

New York University School of Law ( email )

40 Washington Square South
New York, NY 10012
United States
212-998-6672 (Phone)

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