DNA evidence: Helpful, harmful to defendents?

The methodology is not always reliable

Isabell Rivera OW Contributor | 6/27/2019, midnight

Cases like this are nothing new, and although many would argue that it doesn’t fit the norm, mistakes with DNA processing happens more often than many believe. DNA evidence handling sometimes can harm more than it helps. In the U.S. alone there are various cases with innocent people who have been imprisoned based on false positive DNA evidence that put them on the scene of a homicide although they don’t know the victim, or were ever at the scene.

“We all enjoy a good crime drama and although we understand the difference between fiction and reality, the distinction can often be blurred by over-dramatised press reports of real cases,” said EUROFORGEN researcher Denise Sydercombe Court, at King’s College London. “As a result, most people have unrealistic perceptions of the meaning of scientific evidence, especially when it comes to DNA, which can lead to miscarriages of justice.”

In sexual assault cases, DNA does not play a key role anymore, since often times perpetrators use condoms, or make their victims clean themselves after the assault. Therefore investigators take everything into consideration, from toxicology reports, to text messages, or bruises and marks around the genitalia, or otherwise on the body.

Experts also say, “Partial matches are more likely to lead to false positive identification of suspects who are already in the DNA database. Given that less privileged groups tend to be over-represented in DNA databases, this is a serious issue.”

According to a group of scientists, the U.S. uses different methods in policing in different communities. These practices can often result in different rates of incarceration and DNA recording. They also stated that actual drug use is higher in White communities, but “buy and bust” scenarios by law enforcement are more the norm in African-American and Latino communities, which result in disproportionate arrests.

However, there were many cases, such as the Central Park Five case, also known as the “ Jogger Case,” that recently hit the media again. The five innocent Black and Brown boys who faced two-part trials in 1990 were arrested without any physical evidence, including the lack of DNA evidence presence that could link them to the case. They also had no encounter with law enforcement, prior to that case, therefore their DNA was not in the database, yet the jury tried them guilty of the charges.

Even in reverse, where DNA was said to be a match - but wasn’t, and where other evidence proved the opposite, the jury or judge would charge the alleged suspect as guilty.

For instance, the case of Calvin Johnson, who spent 16 years in prison, for a rape he did not commit. He got charged because of eyewitness misidentification, and unvalidated or improper forensic science. However, because of non- DNA evidence in the reinvestigation by the Georgia Innocence Project, Johnson was able to get exonerated since his sperm did not match the sperm present in the rape kit of the victim.

In the case of Chris Tapp, another rape case, the DNA didn’t match, but Tapp confessed—a confession which he later said was coerced by the invesitagors— but the judge and jury dismissed the evidence and gave his confession more weight.