Suspected Gilgo Beach serial killer Rex Heuermann's cheek swab DNA matches a sample collected from a pizza box in a trash can outside his Manhattan architecture firm, prosecutors revealed in court Wednesday morning. 

"It's consistent with our expectations, so that's good," Suffolk County District Attorney Ray Tierney said after Heuermann's court appearance Wednesday. The DA is also the lead prosecutor on the case.

Heuermann's defense attorneys, Danielle Coysh and Mike Brown, had previously tried to block authorities from taking a cheek swab, arguing that prosecutors had failed to show probable cause. The judge disagreed.

REX HEUERMANN'S LAWYER CLAIMS PIZZA BOX DNA DOESN'T SHOW PROBABLE CAUSE IN GILGO BEACH MURDERS

Image on left shows pizza box with partly eaten crust inside, right shows suspected serial killer Rex heuermann entering court wearing handcuffs, slacks, a buttondown shirt and a blazer

An image of the pizza box the FBI allegedly recovered from outside Rex Heuermann's office in Manhattan. Rex A. Heuermann, right, the architect accused of murdering at least three women near Long Island’s Gilgo Beach, appears before Judge Timothy P. Mazzei in Suffolk County Court on Tuesday, Aug. 1, 2023, in Riverhead, New York. (Suffolk County District Attorney's Office, Right: James Carbone/Newsday via AP, Pool)

According to court documents, the FBI observed Heuermann discarding the box outside his Manhattan office before his arrest in July.

With it, lab testing allegedly found DNA matching evidence at the Gilgo Beach crime scene with the body of victim Megan Waterman, 22.

Megan Waterman smiles with bleached blonde hair.

Megan Waterman was 22 years old when she vanished on June 6, 2010, on security video from a Holiday Inn Express hotel in Hauppauge, New York. Suffolk County police found her remains on Dec. 13, 2010 near Gilgo Beach during the search for Shannan Gilbert. (Suffolk County Police Department)

Heuermann has pleaded not guilty to six counts of murder for the deaths of Waterman, Amber Costello, 27, and Melissa Barthelemy, 24.

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File photo of Gilgo Beach murder victim

Amber Lynn Costello’s remains were found near Gilgo Beach, New York on Dec. 13, 2010. (Suffolk County Police Department)

Tierney also indicated that Heuermann may soon be charged in the death of a fourth woman, Maureen Brainard-Barnes, 25, whose remains were found near the other three in the brush alongside Ocean Parkway near Gilgo Beach.

Heuermann has previously been identified as the prime suspect in her death.

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File photo of Gilgo Beach murder victim

Melissa Barthelemy’s remains were found near Gilgo Beach on Dec. 11, 2010. (Suffolk County Police Department)

In addition to the pizza box DNA and a description of the suspect from Costello's former pimp, investigators also used phone records to zero in on Heuermann after a new task force was created to investigate the cold case in 2021.

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File photo of Gilgo Beach murder victim

Maureen Brainard-Barnes’ remains were found near Gilgo Beach on Dec. 13, 2010. (Suffolk County Police Department)

Police discovered the four women's remains while searching for another missing woman, Shannan Gilbert, who vanished after calling 911 in a neighboring beach community on the same parkway. Six other bodies were also recovered nearby.

The discovery process is ongoing. Heuermann is due back in court on Nov. 15. He faces up to life imprisonment without the possibility of parole if convicted.

Gilgo beach sign on Ocean Parkway NY

A road sign directing drivers to Gilgo Beach off Ocean Parkway, about 45 miles east of New York City. (Michael Ruiz/Fox News Digital)

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In the meantime, he is being held without bail at the Suffolk County Jail in Yaphank.

Fox News' Angela Bertorelli contributed to this report.