Experts Offer Concerns Over Forensic Testing in ‘Making a Murderer’ Case

The Netflix series Making A Murderer drew attention to a number of failures in the justice system, from police and prosecutorial misconduct, to the collection and scientific analysis of the physical evidence. A group of four forensic experts have been conducting a year-long evaluation of forensic evidence from the Steven Avery case, and recently wrote an article for the Pittsburgh Post-Gazette which points out a few “striking examples” of potential shortfalls. “Many forensic science methods are inadequately validated, which means they have not been sufficiently tested to establish how well they work and how often and under what conditions they fail,” the experts write. “Avery’s case provides a dramatic example of the uncertainty and confusion that can arise when experts rely on such methods, especially when the court allows the findings to be introduced as scientific evidence at trial.”

Here are the two ways that forensic evidence in the Avery case might have been mishandled.

Forensic Pitfall #1 – Inadequate Validation
A DNA test confirmed that the blood found in Teresa Halbach’s car was a match for Steven Avery. However, his trial attorneys theorized that the blood could have been planted from a vial of Avery’s blood collected by police years before. Blood from the vial would contain a chemical preservative known as EDTA, therefore, if EDTA was detected in the blood found in Halbach’s car, it had to have been planted. The FBI, at the request of the prosecution, quickly developed a new test to detect EDTA in dried blood. FBI expert Mark LeBeau testified that he tested three out of the six blood stains in Halbach’s car and did not detect EDTA, and therefore concluded “within a reasonable degree of scientific certainty” that all of the blood in Halbach’s car did not contain EDTA.

One issue with LeBeau’s conclusion, the experts write, is that the swiftness with which the test was developed. There was no time for the extensive research and analysis needed to even know how often and under what conditions EDTA could be detected in dried blood taken from a decades old vial. Without that research, the experts write, assessing the validity of LeBeau’s conclusion is difficult.

The fact that LeBeau tested only 50 percent of the available samples is also cause for concern. “The absence of evidence isn’t evidence of absence,” the experts write. “If the quantity of EDTA present in the stains was near the threshold of detection, it might have been detected in some of the stains but not others. In fact, if only one of the samples had EDTA above the threshold of detection, there was only a 50 percent chance that it would have been detected in the three analyzed samples.”