A long-awaited and crucial moment in the case against the alleged Gilgo Beach serial killer Rex Heuermann took place Friday in a Suffolk County courtroom.

Judge Timothy Mazzei held a Frye hearing to determine whether prosecutors will be allowed to move forward with critical DNA evidence they say links Heuermann to the killings of seven women on Long Island between 1993 and 2011.

Also known as a "general acceptance" hearing, the legal procedure is used to determine the admissibility of scientific evidence or expert testimony in a case.

Prosecutors called Dr. Kelly Harris to the stand. She is a genome science professor and gave extensive scientific testimony about nuclear DNA. As News 12 reported, Heuermann's defense team is trying to have that evidence dismissed from his trial. Heuermann's lawyer Michael Brown appeared to be skeptical about the witness called on Friday. The Frye hearing will continue on April 2.