A 32-year-old murder case that many considered unsolvable has finally been brought to a resolution – and it all came down to the equivalent of just 15 human cells.
While the techniques that made the achievement possible are not new, what made this case truly extraordinary was the amount of DNA that was available: just 0.12 nanograms. That is less than for any case in history – to put the achievement into perspective, the amount of DNA used by commercially available tests is about 750 to 1,000 nanograms.
Stephanie Isaacson was just fourteen years old when she was sexually assaulted, beaten, and strangled to death on her way to school. DNA evidence from her killer was left on her shirt, but multiple attempts through the years at finding a match proved fruitless. For more than three decades, her case was cold.
However, nine months ago, a Texas-based genome sequencing company called Othram approached the Las Vegas Metropolitan Police Department (LVMPD) with an offer. They had recently received an anonymous donation to be used to fund the investigation of one cold case. It didn’t matter which, as long as it came from the LVMPD.
“Stephanie’s case was chosen specifically because of the minimal amount of DNA evidence that was available,” explained LVMPD Lt. Ray Spencer at a news conference concerning the discovery. “As a result, we have identified Darren Roy Marchand, who has been positively identified as the person who sexually assaulted and murdered Stephanie in 1989.”
DNA analysis has come a long way in the past few decades. What was once the preserve of science fiction can now be bought as a (sometimes ill-advised) birthday present. These commercial DNA tests don’t just tell you about your ethnic background or medical predispositions – they are used in medical research, they’re helping beat the coronavirus pandemic, and yes, they even fight crime. Back in 2018, for example, genetic genealogy techniques helped catch the Golden State Killer who murdered 12 people and raped 51 more throughout the 70s and 80s.
Isaacson’s killer was identified using a similar technique. Over seven months, Othram built a genetic profile from the remains of the DNA evidence, which they compared with ancestry databases. They were able to match the DNA to the cousin of Isaacson’s suspected murderer, and from there, they identified the killer himself – a man previously charged in 1986 with strangling 24-year-old Nanette Vanderberg to death (that case was dropped due to lack of evidence, and the suspect killed himself nine years later).
“When you can access information from such a small amount of DNA, it really opens up the opportunity to so many other cases that have been historically considered cold and unsolvable,” Othram chief executive David Mittelman told the BBC.
While there’s no way to know whether Isaacson knew her killer, Lt. Spencer said that it appeared to be a random attack – known to dramatically decrease the chance of closure.
“I’m glad they found who murdered my daughter,” Isaacson’s mother wrote in a statement read at the news conference. “I never believed the case would be solved.”