DNA testing, heralded for its reliability, can unravel at the edges.

Photo by the University of Michigan

In this month’s magazine issue of The Atlantic, Matthew Shaer explores the state of DNA testing across the United States, finding that the “forensic technique is becoming ever more common — and ever less reliable.” Why?

Traditional DNA analysis — where a one person’s DNA is either matched against a DNA sample from a crime scene, or a crime scene sample is matched against a government database of known suspects — is still heralded as the gold standard of forensics. As a 2009 National Research Council decrying inadequate methods in other forensic disciplines report noted:

no forensic method [other than traditional nuclear DNA analysis] has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source.

However, as Shaer writes, that consistency and reliability still depends on other factors:

The problem, as a growing number of academics see it, is that science is only as reliable as the manner in which we use it — and in the case of DNA, the manner in which we use it is evolving rapidly.

One issue is the variability of standards and procedures across labs. As Erin Murphy, a professor at New York University School of Law, told Shaer “when you start to drill down deeper into the way crime laboratories operate today, you see that the subjectivity is still there: Standards vary, training levels vary, quality varies.” And in a system that is supposed to promote objective assessments, lax standards that give room for subjectivity can mean less reliable and consistent results.

Further, because traditional DNA analysis has been so successful, new, but yet-to-be fully proven DNA technologies benefit from that success and as a result enjoy a societal presumption of reliability and accuracy. The problem, according to Murphy, “with all DNA profiling is that there isn’t skepticism … [t]here isn’t the necessary pressure.” In order for promising new technologies to be accepted by the public, as well as the scientific and legal community, they’ll have to be transparent, she argues.