Fighting “unique” toolmark testimony with science and an amicus brief

Image result for tool marks

Much like bitemark “identification”

“In this case, a toolmark “expert” testified against James Genrich by assuring the jury that several of Genrich’s tools made purportedly unique marks on fragments of the bombs recovered from the crime scene, “to the exclusion of any other tool” in the world. That testimony all but assured Genrich’s conviction. But as this brief describes, the scientific community has now recognized that it is not a forensic discipline. “The reality is that uniqueness is impossible to prove, and is not anywhere near as relevant as some may claim[.]”2”

Read the entire brief filed in The People of the State of Colorado v. James Genrich

Genrich-appellate-filing

About csidds

Dr. Michael Bowers is a long time forensic consultant in the US and international court systems.
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2 Responses to Fighting “unique” toolmark testimony with science and an amicus brief

  1. John Lentini says:

    We need to always distinguish between the “tool marks” made by tools from the “tool marks” made on projectiles by gun barrels. There are far fewer variables with the gun kind. There are many times when the landmarks and the thousands of striations made by a barrel are, in fact, unique.

  2. Brent Ostrum says:

    The brief is well worth reading. Unfortunately, the quote from the introduction of the brief is incomplete and misleading because a full line of text has been omitted. In the original it says “But as this brief describes, the scientific community has now recognized that it is not appropriate to express such a conclusion in the area of toolmarks, or in any forensic discipline.” The line “appropriate to express such a conclusion in the area of toolmarks, or in any” changes the message quite a bit.

    In reality, the scientific community generally has no issue with toolmark examination being considered a forensic discipline. Rather they take exception to conclusions based on claims of ‘uniqueness’, both in that discipline and others.

    Ultimately, the brief argues that the toolmark evidence, as applied in that case, was “unscientific and unsupportable” because “the prosecution did not lay a foundation adequate to establish that, by using the unscientific methodology he purported to rely upon, O’Neil could accurately draw the inference to which he testified.”

    Not being a toolmark examiner I have no comment on the arguments made in the brief but, nonetheless, I think that the mis-quotation is an unfortunate and inaccurate characterization of the forensic discipline of toolmark examination.

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