For nearly 50 years, the murder of Julie Ann Hanson, who was 15 when she was stabbed to death and her body was discovered in a cornfield, baffled investigators in a Chicago suburb.

Detectives came and went, chasing leads and a list of potential suspects that never quite panned out.

But then a breakthrough in the unsolved case came last week, when police in Naperville, Illinois, announced that they had arrested a Minnesota man in the 1972 killing.

The man, Barry Lee Whelpley, 76, who lived within a mile of Julie’s home at the time that she was abducted, was taken into custody Wednesday and charged with three counts of first-degree murder, authorities said.

Police said that genetic genealogy had connected Whelpley, a retired welder who was 27 at the time, to the crime. They would not elaborate on the specific dynamics of what led investigators to him, saying that they did not want to compromise their case against Whelpley, who is being held on $10 million bond.

“This was never a cold case for our police department,” Robert Marshall, the Naperville police chief, said during a news conference Friday. “We were all conscious of Julie’s murder, looking for the killer.”

It was not immediately clear if Whelpley, of Mounds View, Minnesota, had a lawyer. Authorities were waiting to extradite him to Illinois.

The breakthrough, like more than 40 other arrests in long-unsolved cases, is once again being attributed to the science of genetic genealogy. The most notable such case led to the arrest of the so-called Golden State Killer, Joseph James DeAngelo. He was sentenced to life in prison without parole for 13 murders and nearly 50 rapes that terrorized California in the 1970s and ’80s.

Genetic genealogy typically involves cross-checking DNA evidence with ancestry records, including those on popular ancestry database websites. Marshall said that several private labs and companies had helped with the investigation, which spanned the careers of a number of detectives.

“This brutal crime haunted our community for many, many, many years,” he said.

On July 7, 1972, Julie borrowed her brother’s bike to go to a baseball game and never returned home, authorities said. She was reported missing the next day, and her body was found in a cornfield in Naperville, which is about 30 miles west of Chicago.

Julie’s parents have died, but other family members, some of whom attended the news conference Friday, thanked investigators in a statement that was read by Marshall.

“As you might assume, it has been a long journey for our family,” the statement said. “We are forever grateful to all those who have worked on this case throughout the many years.”

James W. Glasgow, the state’s attorney for Will County, said that Julie’s case was the last of three murders of girls in the Naperville area in the 1970s that investigators were able to solve.

“So we have lived these crimes,” Glasgow said. “They’ve been over our shoulder our entire careers.”

Although there was speculation that the man convicted in the other two murders had also killed Julie, investigators did not believe that was the case, he said.

“These guys never rested,” he said of the investigators, “never put the file to the side.”

This article originally appeared in The New York Times.

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