32-year-old homicide solved with smallest DNA sample ever

Stephanie Isaacson

A murder case that took place 32 years ago, which many considered unsolvable, has finally been unraveled (and all thanks to the smallest DNA sample ever used to decipher a case).

According to the website IFLScience, although the techniques that made this outcome possible are not new, what made the case really extraordinary was the amount of DNA used to find the culprit: only 0.12 nanograms. (the equivalent of 15 human cells).

In 1989, 14-year-old Stephanie Isaacson was raped, beaten and strangled to death on her way to her school in Las Vegas, USA. The killer’s DNA was found on the girl’s sweater, but all attempts made over the years to find a match were unsuccessful.

But about nine months ago, a Texas-based genome sequencing company, called Othram, approached the Las Vegas Metropolitan Police Department (LVMPD) with an offer.

The company explained that it had recently received an anonymous donation that would have to be used to fund the investigation of a filed case. It didn’t matter which one it was, as long as it came from LVMPD.

“Stephanie’s case was chosen specifically because of the minimum quantity available DNA evidence,” Lieutenant Ray Spencer explained at a press conference.

“As a result, we identified Darren Roy Marchand, who was positively identified as the person who raped and murdered Stephanie,” he added.

Over the course of seven months, Othram built a genetic profile from the DNA remnants, which it compared to ancestry databases. That’s how investigators were able to match the DNA with that of a cousin of the alleged killer.

From there, they identified the author of the crime, a man who had also been accused, in 1986, of strangling to death Nanette Vanderberg, at the time 24 years old (the case was shelved for lack of evidence and the suspect committed suicide nine years later).

“When we are able to access this kind of information from such a small amount of DNA, it just shows that it really opens up an opportunity for many more cases that have been shelved and deemed impossible to resolve,” said Othram Chief Executive David Mittelman to the British chain BBC.

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