A battle is brewing over whether a key piece of DNA evidence will be allowed into testimony in the Gilgo Beach serial killer’s case.

A motion was filed Tuesday by the defense for what is called a Frye hearing.

Rex Heuermann’s attorney is asking a judge to exclude expert testimony related to nuclear DNA results obtained from hairs found at six crime scenes from the trial.

Prosecutors say the genetic testing done on hairs found on the victims connects them to Heuermann.

However, Heuermann’s lawyer says the methods done by a California lab have never been presented in a New York court.