Lancester County, Pennsylvania - The DNA found on a discarded coffee cup provided authorities with the evidence they needed to make an arrest in a 1975 murder case that had rattled a community for decades.

The heinous murder of Lindy Sue Biechler haunted the county and investigators of Lancaster, Pennsylvania, for 46 years.

But as of Monday, as the New York Times reported that the oldest unsolved case of the county is now closed, thanks to the advances of DNA forensics and a discarded coffee cup.

At a press conference Monday, the Lancaster County District Attorney’s Office and the Manor Township Police Department announced that they had arrested David Sinopoli (68) of Lancaster County on homicide charges.

Lindy Sue Biechler was murdered in 1975 in her apartment. Her aunt and uncle found the bloody scene and the body of their 19-year-old niece. Biechler, a recently married flower shop clerk, had been stabbed 19 times with two different knives from her own kitchen. One knife was still in her neck.

Four decades later, Heather Adams, the Lancaster County district attorney, said, "Lindy Sue Biechler was on the minds of many throughout the years. Certainly, law enforcement has never forgotten about her."

The evidence at the scene in 1975 suggested that the killer wasn't trying to rob his victim.

Adams said Biechler was found with unzipped jeans that exposed her underwear, which had semen on it. Investigators took DNA samples from the scene.

Until now, those samples only helped Investigators clear dozens of suspects, not find the perpetrator.

Though David Sinopoli lived in Biechler's four-unit apartment building at the time of her murder, he didn't become a suspect until after 2020, thanks to what genetic genealogist Cece Moore called a "highly scientific tip" during Monday's press conference.

Moore, who works for Parabon NanoLabs, started working with the DNA profile from the 1975 murder in December 2020. Her genealogical research led her to believe that whoever was responsible for Biechler's death had family members who recently immigrated from Italy and, more specifically, from the Gasperina area. Moore's combing of public databases and newspapers led her to tip off investigators about David Sinopoli.

Authorities started trailing Sinopoli, and in February 2022, they followed him to Philadelphia International Airport. There, they obtained his DNA from a coffee cup he threw into the trash before boarding a flight.

In June, the DNA results came back, and the DNA on the cup matched samples taken from Biechler’s underwear. This led to David Sinopoli's arrest and subsequent charges of murder.

On Monday, Adams thanked the team that worked on the case for decades, calling the investigation "a never-ending pursuit of justice for Lindy Sue Biechler."