There was a tip about the suspect's pickup truck, multiple burner phones, threats to victims’ families, and finally, the DNA evidence to tie it all together.
What DNA evidence was found 13 years ago?
Detectives discovered the bodies wrapped in hunting camouflage burlap within a quarter mile of each other on a stretch of Gilgo Beach.
At that time, they made a discovery that would prove crucial to the case – five hairs found on three victims.
But frustratingly, more than a decade ago, the hairs were so degraded that they couldn't be tested, but importantly, they weren't discarded, and that has changed everything now.
The technology is vastly improved, and with advancements specifically in what's known as mitochondrial DNA, there was a breakthrough.
"There's so much more mitochondrial DNA per cell than there is nuclear DNA, and because of the structure, the mitochondrial DNA, it's circular," forensic expert Cynthia Cale said. "So, it's self-contained so it's protected better from environmental factors"
What is mitochondrial DNA?
Mitochondrial DNA is inherited from your mother, and importantly, it also doesn't degrade as quickly over time. It's become valuable studying ancestry and evolution, and for cracking the Gilgo Beach case wide open.
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"When you have like a hair sample, what you want is the root of the hair that contains mostly the best source of the nuclear DNA," Cale said. "If you don't have that route, and you have to rely on the shaft of the hair, the mitochondrial DNA analysis is really your only option to get any kind of profile from that sample."
How was Heuermann linked to the murders?
Utilizing the tools, investigators say they were able to confirm one of the hairs on the body was Heuermann’s by matching it to a pizza box he'd thrown away – matching his DNA through a leftover pizza crust.
So, what happens now?
Over the objections of his defense team, a Suffolk County supreme judge ordered Heuermann to provide a DNA swab for even more analysis, and to possibly reinforce the pizza crust findings.
Without the direct DNA sample, in theory, defense attorneys could argue at trial the DNA on the pizza crust came from someone else.
The swab will also allow a sample to be entered into a state and national database to see if any other crimes are connected.
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"Once we generate a profile from an alleged suspect that can go into the national database, which gets searched against other cases nationwide, so if he potentially committed any crimes elsewhere, that could link him directly to those cases," Cale added.
DNA results cannot be taken in isolation. They are often one piece of the puzzle, linking the evidence to the suspect, or in this case, a suspected killer who's haunted the community for a long time.