Help v. harm: How a "lookup table" for evaluating DNA evidence given activity-level propositions could lead to wrongful convictions.

DNA testing methods have become incredibly sensitive. Many court stakeholders have accordingly shifted their focus from questions about "who is the source of the DNA?" to "how did the DNA get to be where it was found?" Given this shift, some in the forensic DNA community have urged courts in the United States to permit testimony interpreting DNA evidence given activity-level propositions (ALP). These advocates assert that ALP reporting and testimony will "help" courts answer the relevant questions in their cases. This assertion requires scrutiny. Examinations of wrongful convictions teach us that forensic experts can do irreparable harm when attempting to help courts answer difficult questions. The potential that ALP reporting and testimony will contribute to miscarriages of justice in U.S. courts must be considered. The commentary in this article critically assesses the claim that ALP reporting and testimony will help courts in the United States reach the correct outcome. We do so by analyzing an activity-level "lookup table" that was recently published by advocates of ALP reporting in a paper titled Interpreting DNA under fingernails given activity level propositions. Our analysis considers the potential that LRs reported in the lookup table will mislead end-users. We also consider the vulnerability of U.S. courts to wrongful convictions based on overstated forensic science testimony. Our analysis ultimately reveals that application of the lookup table to casework in the United States may not help end-users reach the correct outcome, and may, in fact, increase the risk of wrongful convictions.