Suffolk County District Attorney Ray Tierney said "cutting edge" advances in DNA testing led to overwhelming statistical matches between samples taken from the "Gilgo Four" victims and the family of suspected Long Island serial killer Rex Heuermann.

Speaking to reporters after Heuermann’s arraignment on a fourth murder charge Tuesday, Tierney said the latest test results helped bring charges for the death of Maureen Brainard-Barnes, 25, and strengthens the case against Huermann in the other three murders.

Before an indictment for Brainard-Barnes' death, Heuermann already faced murder charges in the deaths of Melissa Barthelemy, 24, Megan Waterman, 22, and Amber Costello, 27. All four women were found in the brush near Gilgo Beach, east of New York City.

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Heuermann had been under surveillance for more than a year before police arrested him outside his Manhattan architecture firm, his attorney Mike Brown said outside the courtroom earlier. 

Court documents revealed Tuesday that detectives also tailed his daughter, who is not a suspect but whose DNA was transferred to one of the victims – allegedly by her father while she was on a beach vacation. 

Detectives not only collected DNA samples from the suspected killer and his wife. They also followed Victoria Heuermann on a train ride and picked her discarded "Monster Java" can out of the trash. Then lab testing allegedly matched it to a sample collected from victim Amber Costello.

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While investigators believe Victoria Heuermann was out of town during the murder and Tierney noted she was only 13 at the time, it is alleged her hair was transferred to Brainard-Barnes' remains by her father on a piece of tape used to bind the victim.

Tierney told reporters after the hearing investigators charged Heuermann with Brainard-Barnes' death months after the other victims because they were waiting for the results of "cutting-edge" SNP process testing, which he said came back an overwhelming match in the case.

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"We had the mitochondrial results with regard to the female hair found at the Costello burial site, and that was consistent with the genetic profiles of both Asa [Ellerup] and Victoria Heuermann. And that was to an exclusion of 99.98% of the rest of the population," Tierney said. 

"If you remember the science of mitochondrial DNA, unlike nuclear DNA, you inherit that solely from your mother. So a mother and a child will have identical mitochondrial DNA profiles … We now have nuclear DNA profiles on all five of the question hairs, and we use this using the snip or SNP process."

The nuclear results show a staggering high probability of a match, Tierney explained. 

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"The way that number is expressed, that's scientific expression, I'm told. So, that's basically 2.374 and you add 48 zeros to that," he said. "So that's a number so large … a name for it doesn't even exist."

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While the superseding indictment shows investigators continue to build their case, retired NYPD Inspector Paul Mauro told Fox News Digital Tuesday the latest filings were "nothing earth-shattering."

However, they amount to stronger evidence than was publicly known before Tuesday's arraignment on the fourth murder charge, especially the connection between Victoria Heuermann's hair and Costello, which he said "confirmed" earlier suspicions.

The Costello connection is also important because her pimp is the lone eyewitness identified in public court filings who described an altercation with an "ogre" matching Heuermann's physical description and helped lead police to the suspect vehicle, a green Chevrolet Avalanche like the one authorities discovered from the suspect's brother's home in South Carolina.

After Heuermann's arrest in July, investigators seized his burner phones and other devices, Tierney said, ultimately finding more evidence in the case that helped them land an indictment for Brainard-Barnes' death.

Among the new files, police obtained cellphone billing records that Tierney said show Ellerup and her children were in Atlantic City, New Jersey, when Brainard-Barnes went missing July 9, 2007. Heuermann joined his family there July 13.

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Ellerup's attorney, Bob Macedonio, told Fox News Digital the family had no idea Victoria Heuermann was being followed until the bail application came out Tuesday.

"The murders of all four victims occurred at times when Defendant Heuermann’s wife and children were traveling out of state, which allowed Defendant Heuermann unfettered time to execute his plans for each victim without any fear that his family would uncover or learn of his involvement in these crimes," prosecutors wrote in a bail application.

Despite that, Heuermann allegedly transferred his family's DNA t to the victims, where it sat for years before genetics testing had improved enough for police to make use of it.

Investigators found Brainard-Barnes bound with three leather belts, one around her ankles. Hair on that one showed a genetic link to Ellerup, according to the new filing. Waterman's remains were bound in duct tape, according to prosecutors, and a hair recovered from her bindings also matched Ellerup. A male hair in the burlap material used to conceal her remains allegedly matched Heuermann directly, according to court filings.

Costello, who was bound with tape and a burlap material, also had transferred hair, according to the superseding indictment – this time from Victoria Heuermann, the suspect's daughter, who was 13 at the time of the slaying and away with her mother.

Other evidence unveiled in the latest filings include details about how each of the victims was bound and how police recovered additional burner email accounts under fake names like "Andrew Roberts" and "Sandbagger303," which were linked to searches for violent pornography and news updates on the Gilgo Beach cold case investigation.

Heuermann faces three counts of first-degree murder and four counts of second-degree murder. He is being held without bail and due back in court Feb. 6.

The Gilgo victims were among nearly a dozen discovered after police received a haunting 911 call from Shannan Gilbert in 2010 and began searching for her near Oak Beach, a few miles to the east.

Crews looked through the dense brush north of Ocean Parkway for months, uncovering the Gilgo Four and a half-dozen other bodies before they finally found Gilbert's remains.

The other deaths remain under investigation by a grand jury, Tierney said Tuesday.

"With regard to those other bodies and those other murders, the task force will continue to investigate those cases," he added.

Heuermann was born and raised in Massapequa Park, New York. He bought his childhood home from his mother in the 1990s and moved his family there. Neighbors described him as quiet and unassuming, but some said they got creepy vibes from the unkempt home, which has aging siding, twisted flashing along the roof and two-by-fours holding up the front awning.