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DNA evidence: Helpful, harmful to defendents?


The thought of going to trial and being prosecuted without any DNA (deoxyribonucleic acid) evidence seems unthinkable in 2019, but sometimes DNA evidence can actually be more harmful than helpful. In many cases that come to trial, DNA evidence plays a key role, next to confessions, and eye-witness testimonials. However, it’s up to the judge and the jury how much weight DNA evidence receives in comparison to confessions and testimonies.

Since DNA is only 99.9 percent identical—which means we share DNA with everyone else—it’s the 0.1 percent that make us individuals, and therefore unique. With that said, it’s never really a 100-percent match.

According to experts, “while DNA is extremely good at identifying individuals, mistakes have happened. Accurate identification is dependent on a number of factors, including the quality of the DNA sample, the number of genetic markers analyzed, whether the sample was prepared properly, and the ability of those doing the analysis to interpret the results.”

Of course, any discussion of DNA evidence harkens back to the O.J. Simpson case. Although Simpson’s DNA and that of Nicole Brown and Ron Goldman was found at the crime scene and at Simpson’s residence, the forensic work was handled sloppy, causing cross contamination with DNA of the victims, suspect, and the LAPD.

The mishandling of DNA evidence is one of the issues that could lead to errors in finding the suspect. Since DNA travels through talking, sneezing, touching various objects, hugging strangers or shaking hands, it can therefore place a person at locations (or before people) they haven’t visited physically. DNA is also shed through losing hair or skin cells, for some people more than others. An average person may shed up to 50 million skin cells a day.

However, when it comes to DNA testing, a dozen or more genetic markers in the code are used to identify important aspects, such as differences and similarities between people.

According to experts, “The more markers used, the greater the accuracy, but also the cost of testing. The probability of the DNA profiles of two unrelated individuals matching is on average less than one in 1 billion. Even advanced DNA testing, which allows the recovery of minute traces of DNA, cannot prove how the DNA got to a crime scene.”

A good example for DNA transfer is the case of Lukis Anderson. Anderson, a Black homeless man with an alcohol problem, tends to sometimes “blackout” while drunk. But did he commit murder? When he got the news that his DNA was linked to a robbery-homicide case more than 10 miles from his location, he was shocked and confused, but didn’t doubt that he might have done this while being blacked out. It didn’t help either that Anderson had quite a rap sheet full of petty crimes, which put his DNA into the database, and being a minority and homeless made him to be more of a target.

Somehow, Anderson’s DNA got transferred onto  a homicide victim, Ravesh Kumra.

But Anderson had an alibi. On the night of the robbery-homicide, Anderson decided to get drunk and pass out at the store, where the manager called for an ambulance. After the paramedics helped Anderson—who was a familiar face—they received a phone call to go to the residence of Raveesh Kumra, the homicide victim, which likely resulted in the DNA transfer either because of a pulse oximeter slipped over both patients’ fingers, the uniforms of the paramedics, or another piece of equipment. While the actural reason for this circumstance remains unclear, it became apparent that Anderson had nothing to do with the case.

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.

“Just because it’s DNA doesn’t mean it’s good science,” said Prof. Greg Hampikian of Boise State University. He also worked on Johnson’s and Tapp’s case.

Another case Hampikian worked on, was that of Kerry Robinson, who was sentenced to 20 years in relations to a gang rape. Robinson wasn’t identified by the victim, but he knew the man who was identified and whose DNA matched 11 of the 13 alleles (a type of gene resulting from mutation) found in the DNA mix at the crime scene, excluding the victim. As it turned out, the identified suspect Tyrone White made a plea deal with the D.A. and mentioned Robinson to be the other of the three suspects, because he had a grudge against him. However, Robinson only had two alleles in common with the found DNA on the victim’s body, which was “at the borderline of detection,” Hampikian said and who testified that Robinson was “absolutely excluded.”

“It’s hard for a judge to overturn a 15-year-old conviction,” Robinson’s attorney, Rodney Zell said. An appeal judge ruled against Robinson’s appeal.

“Just because it’s DNA doesn’t mean it’s good science,” Hampikian explained. He also worked on Johnson’s and Tapp’s case.

Anderson can be considered lucky, by escaping the death penalty.

“There’s more that’s gotta be looked at than just DNA,” he said in an interview.”You’ve got to dig deeper a little more. Re-analyze. Do everything all over again…before you say ‘this is what it is.’ Because it may not necessarily be so.”

And it’s true, like any human discovery, DNA analysis has its flaws. British forensic researcher Peter Gill, has little uncertainty that the forensic field, which gets a lot of attention and credits to solve crimes, is also responsible for wrongful incarcerations.

“The problem is we’re not looking for these things,” Gill said. “For every miscarriage of justice that is detected, there must be a dozen that are never discovered.”