RIVERHEAD, N.Y. (AP) — DNA from Gilgo Beach serial killing suspect Rex Heuermann’s cheek swab matches the DNA that authorities had previously collected from a pizza crust and used to link Heuermann to one of the victims, prosecutors said in court Wednesday.

Heurmann, 60, was arrested July 13 on murder charges in the killings of Melissa Barthelemy, Megan Waterman and Amber Costello, three of the women whose bodies were found along a remote beach highway on Long island, and has been named as the the prime suspect in the death of a fourth woman.

He pleaded not guilty and has been held without bail at Suffolk County Jail in Riverhead.

At the time of his arrest, prosecutors said they had analyzed DNA from a pizza crust that Heuermann had discarded in a Manhattan trash can and matched it to DNA from hairs found on Waterman’s body. Prosecutors then got permission from the court to collect DNA from a cheek swab of Heuermann as further proof of his link to Waterman’s killing.

“The buccal swab erases all doubt,” Suffolk County District Attorney Ray Tierney told the judge, according to Newsday.

The DNA from the pizza crust had previously been linked to Heuermann’s estranged wife, Asa Ellerup, not to him directly.

The arrest of Heuermann, an architect, came 13 years after police searching for a missing woman found 10 sets of human remains buried in the scrub near Long Island’s remote Gilgo Beach.

Authorities suspected that a serial killer had committed some of the murders but have long said they did not believe all of the victims were killed by the same person. The majority of the killings remain unsolved.

Prosecutors told Suffolk County Court Judge Timothy Mazzei on Wednesday that they had turned over thousands of documents to Heuermann’s defense team.

Heuermann told the judge he has been spending two to three hours a day reviewing the evidence against him.

Heuermann’s lawyer disputed the significance of the DNA sample. “There is nobody on the face of the earth that is credible is going to say that hair is my client’s hair,” defense attorney Michael Brown said outside the courtroom, according to the New York Post.