We have written extensively on this blog and elsewhere about faulty forensic science contributing to wrongful convictions. Numerous instances of crime lab scandals between 2000 and 2008, including multiple instances of fraud and error, resulted in Congress funding an in-depth investigation and review of the forensic science disciplines and related forensic laboratory practice.
The ensuing report by the National Academy of Sciences, entitled "Strengthening Forensic Science In the United States," confirmed the lack of scientific foundation for the majority of forensic science methods.
Even Careful Investigations Can Go Awry
Now, comes a story from the PBS show "Frontline" that reminds us that DNA errors in criminal investigations are not always the result of sloppiness, but can be equally egregious. In the case of Lukis Anderson, a 26-year-old homeless man in San Jose, California, police felt they had been extremely careful in the investigation that led to Anderson being charged (along with two other men) with the 2012 murder of a wealthy investor.
If not for the meticulous work of a defense investigator, Anderson could be another one of the thousands of individuals wrongfully convicted and imprisoned as a result of faulty DNA evidence.
Understanding DNA Transfer
The abbreviated version of Anderson's story is he was treated by paramedics in the back of an ambulance and that same night, the same paramedics responded to the murder victim's home. The paramedics unknowingly transferred DNA from Anderson to the body of the murder victim. When investigators ran tests of the murder victim's fingernails, the DNA from Anderson was discovered and he was arrested on suspicion of murder.
Anderson was held in jail awaiting trial for months. Only the fact that the defense investigator discovered records that Anderson was being treated in the hospital at the time the murder was committed prevented him from being tried and sent to prison.
Tests have shown that DNA is extremely transferable. In fact, some people have characteristics that make them prolific "shedders" (often people with flaky, sweaty or diseased skin). These people leave DNA in almost every environment they enter.
Great Care Needed With DNA Evidence
Only the DNA match led police to name Anderson as a suspect. It led investigators to seek other evidence confirming his guilt. "It wasn't malicious. It was confirmation bias," says public defender Kelley Kulick, who defended Anderson. "They got the DNA, and then they made up a story to fit it."
As the "Frontline" story points out, if the case had gone to trial, jurors likely would have also put too much faith in the DNA evidence. A 2008 series of studies by researchers at the University of Nevada, Yale and Claremont McKenna College found that jurors rated DNA evidence as 95 percent accurate and 94 percent persuasive of a suspect's guilt.
Eleven leading DNA transfer scientists contacted for the "Frontline" story were in consensus that the criminal justice system must be willing to question DNA evidence. They were also in agreement about whose job it should be to navigate those queries: forensic scientists.
Build That Wall
As we have stated in previous posts, in order for crime laboratories to be truly objective, they must be independent agencies and they need to build a "wall" to prevent law enforcement and prosecution influence in evidence testing, which occurs commonly in cases.
Lab results must be replicable, and should be done "blindly" without the analyst knowing details about the case. All tests should be confirmed by a separate team of lab technicians who do not know the identity of the suspect or what the "right" answer should be.