n 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 appropriate to express such a conclusion in the area of toolmarks, or in any forensic discipline. “The reality is that uniqueness is impossible to prove, and is not anywhere near as relevant as some may claim[.]”2 Part I.A of this brief describes how the relevant field of toolmark comparisons lacks scientific research support. While firearms comparisons, which are far more commonly conducted, have been the subject of some studies, toolmarks research is nearly nonexistent. Part I.B describes the “theory” used to advance toolmark identifications in court and explains why scientists have found it unsupported. The section also describes criticism of toolmark comparisons in influential scientific reports that have highlighted problems of overstated testimony, error rates, and lack of research. Part I.C describes toolmark identifications in the courts and how, in recent years, courts have excluded or limited testimony like that presented in the Genrich case. Finally, Part II describes how the flaws inherent in toolmark evidence were borne out in this particular case. In light of the unreliable nature of toolmark evidence, Amici respectfully urge this Court to grant a full evidentiary hearing to review the faulty and wholly unscientific forensic testimony that led to Genrich’s conviction.