In the United States, a murder was solved that was committed in 1989 – for this, the police used a record low amount of DNA. Thirty years ago, this method was not available to law enforcement officers.
The US authorities solved the 1989 Las Vegas murder of a 14-year-old girl using “the smallest amount of DNA.” The case of the murder of Stephanie Isaacson could not be solved, since the new technology did not allow identifying a suspect by DNA: experts were able to extract only a small amount of DNA – the equivalent of 15 human cells.
Police said they were able to identify the suspect using genome sequencing and public genealogy data. As it turned out, her killer died in 1995. “I’m glad they found my daughter’s killer,” Stephanie’s mom wrote in a statement read to reporters at a press conference. “I didn’t believe the case would be solved.”
Thirty-two years ago, Stephanie Isaacson’s body was found near the route she usually took to her school. The police determined that she was attacked and strangled, but could not find the killer.
This year, the police were able to tackle the case again after a donation from one of the local residents. They donated DNA samples left at the scene of the murder to Othram, a Texas-based genomic sequencing laboratory. She specializes in cases that have not been solved for over 10 years.
Typical consumer DNA kits are 750 to 1000 nanograms per sample. These samples are uploaded to public sites specializing in pedigree or health. But crime scenes can only contain tens of nanograms of DNA. In this case, only 0.12 nanograms were available for analysis – about 15 cells.
Using the databases, the researchers were able to identify the suspect’s cousin. They ended up matching DNA with Darren Roy Marchand. Marchand’s DNA was also found in the archive to confirm the match. He was never convicted and committed suicide in 1995.