Suffolk County District Attorney Ray Tierney sat down with News 12 for an exclusive interview following the sentencing of confessed Gilgo Beach serial killer Rex Heuermann, marking the end of a case that plagued Long Island for decades.

The prolific serial killer, who preyed upon women from 1993 to 2010, was sentenced on Wednesday to life in prison without parole for strangling eight women to death. Pieces of their remains were scattered along Gilgo Beach and other parts of the island, sparking the search for the killer. It was one, if not the most high-profile, investigation in the county's history.

Heuermann pleaded guilty in April to the murders of Melissa Barthelemy, Megan Waterman, Amber Costello, Maureen Brainard-Barnes, Jessica Taylor, Sandra Costilla and Valerie Mack. As part of his plea agreement, he also admitted to the killing of Karen Vergata.

In his wide-ranging conversation with News 12, Tierney acknowledged failures in earlier investigative efforts, offering an apology on behalf of Suffolk County. Even so, he emphasized the strength and perseverance of the victims’ families, who remained resolute throughout the long and painful pursuit of justice.

When asked whether Heuermann would have admitted to the killings without the weight of the evidence against him, Tierney was direct.

“No,” he said. “There was a tremendous amount of discovery...Without that strong case, I don't think we'd be here."

As for the turning point in the trial, the DNA evidence and its impact down the road, Tierney said the investigation was built on a wide range of evidence, including phone and financial records, his planning document and mementos he kept. He said advanced forensic analysis played a part but will be even more important going forward.

"This is the future of DNA and we're at the cutting edge here in New York State."

Tierney said this was the first time that type of SNP DNA analysis was deemed admissible in New York State and possibly the third in the United States.

Despite the years-long investigation, Tierney said he only met Heuermann once - during a pre-plea proffer session.

“The defendant is an individual who’s used to hiding certain aspects of himself,” Tierney said. “And I saw that. His demeanor was consistent with that.”

As for the victims’ families, Tierney avoided suggesting that the sentencing would bring true closure.

“Closure is a tough word,” he said. “There will never be closure for these families.” Still, he acknowledged the significance of the moment — after years of waiting, loved ones were finally able to tell their stories in court and confront the man responsible.

Their resiliency showed during their "powerful" victim impact statements.

Heuermann spoke briefly after the poignant remarks.

"There are no words I can say. I am responsible for all that was said in this room today. The words I say have no meaning and I'm going to leave it there at this time."

When asked whether the case is now fully over, Tierney said Heuermann has limited rights to appeal.

"He waved his appeal, so that's always possible, but for the most part - absent a reversal on appeal, which seems unlikely - this case, this indictment is over."

READ MORE: ‘You are a coward.’ Judge sentences Gilgo Beach killer to life in prison without parole