DNA's Big Moment? The O.J. Simpson Trial - OZY | A Modern Media Company

DNA's Big Moment? The O.J. Simpson Trial

DNA's Big Moment? The O.J. Simpson Trial

By Fiona Zublin

The O.J. Simpson murder trial turned DNA into a buzzword.
SourceGetty Images; composite by Ned Colin


Before CSI, there was that bloody sock found in the NFL star’s house.

By Fiona Zublin

Near the beginning of Jurassic Park, a Texas-accented cartoon character known as Mr. DNA explains to park visitors what DNA is and how it was used to clone dinosaurs. That was in 1993, when DNA wasn’t a buzzword. The O.J. trial had yet to add it to the lexicon.

When it came time for jurors in the 1995 trial of O.J. Simpson to learn about DNA, there was no colorful, cheery mascot. Just Dr. Robin Cotton, director of Cellmark Diagnostics, who appeared as an expert witness for the prosecution. She was there to link blood from the murdered Nicole Brown Simpson — O.J. Simpson’s ex-wife — to the defendant’s car and clothing, and to prove that O.J. Simpson’s blood was present at the murder scene. Cotton explained DNA like so: “DNA is correctly described as a polymer, that is, it’s a long series of components that are all attached together, and it’s basically our cellular alphabet.” The definition was dry and somewhat impenetrable, even to viewers in 2019 who have a much better understanding of DNA. But her testimony was riveting too. 

“It was the start of the DNA age, it’s what led to all the CSI [crime scene investigation] shows, because it was high-enough drama — even in its almost infinite tedium of questioning — that people actually tuned in every day,” explains Greg Hampikian, a forensic DNA expert and founder of the Idaho Innocence Project. “It inspired me to become more interested in forensics and possible errors in forensics. Those errors still go on to this day.”  

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Dr. Robin Cotton explains DNA to the jury. 

Source Getty Images

After the case was concluded and Simpson was acquitted of double murder, the overriding media narrative was that the jury simply didn’t understand DNA as a concept and thus discounted the evidence. But the truth was more complicated, argued a paper published a year after the trial by law professor William C. Thompson, who had worked with the defense team. Thompson laid out the case that the defense hadn’t argued against the validity of DNA evidence, just against what they claimed was mishandling of it by the Los Angeles police. Whatever the reason the jury had rejected the DNA evidence presented, DNA analysis — which scientists had fought to get admitted to courtrooms in the first place — had arrived.

A 2017 study of 200 mock jurors found that people presented with DNA evidence were twice as likely to convict.

The O.J. trial was followed by the so-called “CSI effect.” The term first coined in 2004 posited that the post-O.J. boom in televised crime procedurals that focused on forensics and scientific evidence, such as the CSI franchise, caused actual juries packed with informed citizens to expect DNA tests and scientific evidence from every crime scene (and to refuse to convict without such backup). But despite an enormous number of articles about the CSI effect, research has disputed that it influences the outcome of trials: A 2008 article in the National Institute of Justice Journal found that while CSI viewers did have higher expectations of scientific evidence than their peers who didn’t watch crime shows, they weren’t any less likely to convict when such evidence wasn’t present. Still, 75 percent said they expected to see DNA evidence in every sexual assault case.

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This DNA film, projected as evidence during the O.J. trial, linked Simpson to the murders of his ex-wife and her friend Ronald Goldman, according to Cotton. The black smudges reflect the banding patterns of Simpson’s genetic material (highlighted by the pink arrows).

Source Getty Images

And today? A 2017 study of 200 mock jurors found that people presented with DNA evidence were twice as likely to convict. But that evidence isn’t always accurate: In a 2013 study, researchers gave 108 different labs a sample of four people’s DNA and asked them to determine whether genetic evidence of one particular crime suspect was present in the sample. In all, 70 percent of the labs came back with a false positive. And that’s before factoring in the risk of contamination or outright tampering by law enforcement — as some still contend happened in the Simpson case.


The Simpson jury was skeptical of the prosecution’s emphasis on DNA, perhaps because the technology at that time was new and unfamiliar. But trusting in DNA too much, when samples are routinely mishandled and misinterpreted, could cause further miscarriages of justice. “There are these cold cases where all you have is DNA and yet somebody gets convicted,” Hampikian says. “You should have other corroborating evidence.” 

Despite television’s flaws, Hampikian says, it has the potential to educate people about DNA and some of the science surrounding criminal justice. “The CSI shows do a much better job than Columbo did for me. They actually do present a little more of the science,” he says. Still, he’s quick to add, “I don’t think they show enough blunders, which happen all the time, or enough innocent people being accused.” For that, viewers can tap the burgeoning true crime genre, filled with stories about people falsely accused and wrongfully imprisoned — or they could watch American Crime Story, the hugely popular re-enactment of the Simpson trial itself. Perhaps Marcia Clark could’ve used Mr. DNA on her team …

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