Team 12 Investigates has uncovered more details on how prosecutors continue to build their case against Rex Heuermann, who was arrested for the murders of three Gilgo Beach victims.

Further coverage: Task force investigating Gilgo Beach murders identifies Jane Doe No. 7

DNA evidence can be crucial in the investigation and prosecutors said they need more. After Heuermann’s arrest, his wife, daughter and stepson voluntarily provided cheek swabs for DNA analysis. However, Heuermann still has not.

In a motion filed in criminal court this week, the Suffolk County District Attorney’s Office requested a cheek swab from Heuermann to help build his conclusive DNA profile.

“The most informative kind of DNA analysis is autosomal analysis, which is a fancy term that basically will give you the identity of an individual,” said Dr. Lawrence Kobilinsky, forensic scientist and professor at John Jay College of Criminal Justice.

As News 12 has reported, Heuermann’s DNA found on discarded pizza crusts and a napkin matched the DNA of hairs found on the body of Gilgo Beach victim Megan Waterman. However, there is a problem relying solely on that type of DNA, which is mitochondrial DNA.

“It’s not a unique identifier by no means because mitochondrial DNA is inherited maternally,” said Dr. Kobilinsky. “A person has the same mitochondrial DNA as his mother, grandmother, niece, any female relative and siblings. By and of itself, mitochondrial DNA can be challenged simply because the nature of it is to produce a statistic that is not extraordinarily significant.”

Without a DNA sample taken directly from Heuermann’s mouth, as opposed to items such as a water bottle or partially eaten pizza, forensic biologists at the Suffolk County Crime Lab are limited in how they can testify at trial regarding Heuermann’s DNA profile.

According to the criminal court documents, forensics biologists would only be able to reference the pizza crusts and napkin as believed to be “used or touched” by Heuermann and would not be allowed to say it is his DNA profile.

“If the defendant’s DNA from a buccal swab sample matches the mitochondrial DNA profile developed from the hair recovered from Megan Waterman’s remains, there is scientific evidence of the Defendant’s contact not only with Ms. Waterman and where her remains were discovered, but also with the burlap utilized to restrain and transport her human remains,” Assistant Suffolk County District Attorney Michelle Haddad said in the court filings.

Prosecutors also argued that a denial of a cheek swab could deprive Heuermann of a crucial defense at trial if his DNA from the swab does not match the DNA profile from the pizza crusts and napkin.

The defense, which did not return a request for comment, has until next week to oppose the motion. Otherwise, Heuermann will have to provide a cheek swab by August 15.