Discarded cigarette butt helped investigators solve 52-year-old mystery of who killed a Vermont school teacher

• For 52 years, the murder of Vermont school teacher Rita Curran remained unsolved.
• The case was reopened in 2019. Forensic testing of a cigarette butt led detectives to the answer.

For more than half a century, the mystery of who killed a 24-year-old Vermont school teacher remained unsolved.

But the discovery of a discarded cigarette butt, found near the victim's body, has now led investigators to the man they say killed Rita Curran 52 years ago.

In the early hours of July 20, 1971, police were called to an apartment in Burlington, Virginia, after Curran's roommate found the school teacher's body, ABC News reported. Police said Curran was sexually assaulted and strangled.

Hundreds of tips were investigated at the time, but to no avail, and the case went cold. However, in 2019 the Burlington Police Department reactivated it.

Several items that had been kept in storage, including a cigarette butt that had been found on the floor next to Curran's body, were sent to a forensic lab in New York for testing, the Burlington Free Press reported.

A man's DNA was found on the butt, but it didn't match anyone in the national database of felons' DNA, or any of the main suspects, according to local media.

The detectives then sent the genetic material to a company that holds data submitted by the public for commercial DNA testing, the Free Press reported.

Within hours, CeCe Moore, a scientist and genealogy expert at Parabon Nanolabs, was able to match the DNA to William DeRoos, she told the Free Press.

"The DNA evidence ended up being so incredibly key and they couldn't have possibly imagined the power that we would have at this time to actually use that to narrow it down to one person," Moore said.

DeRoos, who died of a drug overdose in 1974, was 31 at the time of the murder and lived above Curran in an apartment. Shortly after the murder he left his then-wife and moved to Thailand to become a monk, according to the Free Press.

DNA testing of Curran's coat confirmed that DeRoos had committed the murder, the outlet said.

At the time of the murder, detectives had spoken to DeRoos and his then-wife Michelle, but they said they had not seen or heard anything.

In a recent police interview, the ex-wife said she had lied about her husband leaving the apartment that night, per ABC News.

Detective Thomas Chennette, who interviewed Michelle, said he thinks she lied because she was "naive" and "in love."

During a press conference on Tuesday, Jim Trieb, who heads up Burlington's Detective Services Bureau, said he was confident that DeRoos was responsible for the murder.

"Because he died in a hotel room of a drug overdose he will not be held accountable for his actions, but this case will be closed," Trieb said, according to ABC News.

Curran's brother, Tom, also speaking at the press conference, said: "I don't think so much about the guy who did this as I do about Rita, my parents, and what they went through. I pray to Rita and I pray to my parents."