By Lauren Leamanczyk, WBZ-TV

BOSTON (CBS) – Detective Phil DiNatale never doubted for a moment that Albert DeSalvo was the Boston Strangler. He was one of the key investigators assigned to track the case and now his son is glad DNA evidence might prove his father right.

READ MORE: Which Towns Got At Least 1 Inch Of Snow During First Winter Storm Of The Season?

Detective Phil DiNatale investigated the 'Boston Strangler' case.

Detective Phil DiNatale investigated the ‘Boston Strangler’ case.

John DiNatale has a binder full of letters that the alleged Boston Strangler wrote his father. Between the years 1967 and 1968, the confessed serial killer and the detective were pen pals. DeSalvo was serving a life sentence for sexual assault at the time.

“Inside the mind of a serial killer begging for help,” John DiNatale says as he reads the handwritten notes.

For years DiNatale has bristled as victims’ families and authors undermined his father’s work, claiming the DeSalvo confession was a fraud.

Still, he says his father did not need vindication. These people he says know nothing about a murder investigation.

READ MORE: One Dead After Violent Dorchester Crash That Ripped Bed Off Pickup Truck

“I think it’s great that the police department has picked this up and done what they’ve done because it certainly brings closure to a lot of people, but there were a lot of great detectives who worked on that case back then,” DiNatale told WBZ.

His father spent 60 hours a week working the case. And when Albert DeSalvo confessed to Attorney F. Lee Bailey, Detective DiNatale spent weeks tracking down the details.

“There was not a doubt in his mind that Albert was the Strangler,” says the younger DiNatale. “Albert knew too much that only the Strangler could have known.”

Bailey also believed the confession. The lawyer says DeSalvo was willing to be studied so others could understand the mind of a serial killer.

“When we have people running around shooting at other people and we have no idea how to identify beforehand and that’s what Albert could have otherwise contributed,” Bailey said Thursday.

DeSalvo’s desire for psychological treatment and study was a constant theme in the letters he wrote his detective pen pal. In one letter he writes, “I’m no different when you think about it than a radiator in a room without a safety valve.”

MORE NEWS: Wellesley Police Investigating String Of Overnight Burglaries At Unlocked Homes

In another he says he wishes “people would wake up and realize it could happen to any one of them.”