With more copies of mitochondrial DNA available, there is greater...

With more copies of mitochondrial DNA available, there is greater likelihood that it can be used for forensic analysis, said W. Richard McCombie, the Davis family professor of human genetics at Cold Spring Harbor Laboratory. Credit: Cold Spring Harbor Laboratory

For more than a decade, Suffolk Police investigators held onto a strand of hair recovered in 2010 from beneath the skeletal remains of Gilgo Beach victim Megan Waterman, not knowing whether it contained the clues to find her killer.

Still, they were frustrated. The limits of DNA technology 13 years ago kept the strand from being properly tested. Meanwhile, it remained in the custody of the Suffolk County medical examiner as police investigators tried to be patient, continuing their search for evidence while waiting for the science to catch up with the clues.

That patience appears to have paid off. When forensic investigators used updated genetic testing technology earlier this month, they concluded that a piece of DNA from the hair strand — known to scientists as mitochondrial DNA — allegedly was linked to Rex A. Heuermann, the Massapequa Park man accused of killing Waterman and two of the other three women whose bodies were in found in 2010 in the Gilgo Beach area. 

Mounting evidence

That discovery, combined with other evidence, and concerns about Heuermann’s continuing interest in sex workers, led the Gilgo Beach task force to arrest and charge him on Thursday.

WHAT TO KNOW

  • Updated DNA testing technology led Suffolk Police investigators to allegedly link Rex A. Heuermann to at least three Gilgo Beach killings.
  • The mitochondrial DNA found in a hair at the Gilgo Beach crime scene allegedly matched DNA retrieved from Heuermann's pizza crust.
  • Mitochondrial DNA can survive longer than nuclear DNA, and with more available, there is greater likelihood that it can be used for forensic analysis.

“The mitochondrial DNA was obviously a big part of the case,” Suffolk County District Attorney Ray Tierney said Tuesday in a telephone interview.

It is a basic principle of human genetics that unlike nuclear DNA, which comes from the nucleus of a human cell and is passed along to a person from both parents, mitochondrial DNA in a cell comes only from the maternal side. It also has a greater chance of surviving contamination and takes longer to deteriorate.   

There is also more mitochondrial DNA than nuclear, according to experts. With more copies of mitochondrial DNA available, there is greater likelihood that it can be used for forensic analysis, said W. Richard McCombie, the Davis family professor of human genetics at Cold Spring Harbor Laboratory.

In cases where there is degraded genetic evidence with compromised nuclear DNA, the smaller and more hearty mitochondrial DNA can be a fallback for investigators in 2023.   

“Each of our cells have many mitochondria. Each has its genome," McCombie said. “Because we have so many of them in ours cells … there are many more copies than nuclear DNA.”

DNA analysis: room for improvement

Mitochondrial DNA analysis has been around for decades, having been used to identify a child victim of the Titanic as well as in other historical cases, said Colleen Fitzpatrick, a genetic genealogist who founded the California-based firm Identifinders. 

It was even used in the 1990s to identify the remains of the czar of Russia and his family after their executions in 1918, McCombie said.

Even so, he added, the technology needed room to improve beyond what it was in 2010.

“The instruments are much more sensitive,” McCombie said of the testing technology now compared to 13 years ago. And sequencing of DNA has improved to the point where instead of requiring a bulk sample of many cells to get enough DNA, only a single cell may now be required, he said.

In the Gilgo Beach case, the hair found on Waterman’s remains, which the Suffolk crime laboratory couldn’t fruitfully analyze years earlier, was submitted to an outside laboratory identified in court papers only as “Forensic Laboratory # 1." In July 2020, the lab generated a mitochondrial DNA profile of a male, someone part of a special genetic group but whose identity was unknown.

Matching with Gilgo Beach victim

Three years later, investigators had zeroed in on Heuermann as a suspect, based on cellphone records and his ownership of a truck like one a witness identified as being linked to the disappearance of one of the Gilgo Beach victims. But they still needed his DNA to test for a link to the hair strand, so investigators surveilled Heuermann and recovered a piece of pizza he had discarded in Manhattan. 

From the pizza, another laboratory, identified in court papers as “Forensic Laboratory # 2," did an analysis — and on June 12 came up with a mitochondrial DNA profile showing it was the same as that of the hair found on Waterman’s remains. An analysis of the DNA excluded 99.96% of the North American population and thus determined that Heuermann “cannot be excluded from the male hair” found at the Waterman crime scene, court records stated.

“The good thing about mitochondrial DNA is it is found in hair and is hardier than nuclear DNA,” Tierney said, adding that the keratin in the surface of hair can serve to protect the mitochondria within the shaft.

Heuermann, 59, who owns an architectural firm in Manhattan, has been charged with three counts each of first- and second-degree murder in the deaths of Waterman, Melissa Barthelemy and Amber Costello. He pleaded not guilty at his arraignment in Suffolk County Court in Riverhead on Friday.

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