A 72-year-old  has been convicted of killing a 7-year-old Illinois girl five decades after the crime.

On Friday, the man, 72-year-old Jack McCullough, who was a neighborhood teen at the time, was pronounced guilty of the 1957 kidnapping and murder of Maria Ridulph.

According to the Huffington Post, it was one of the oldest unsolved crimes in the United States to make it to trial.

"A weight has been lifted off my shoulders," said Kathy Chapman, 63, who was playing with Maria in the snow on the night of Dec. 3, 1957, before she disappeared. "Maria finally has the justice she deserves."

In her testimony, Chapman explained how McCullough approached the two girls and gained Maria's trust by giving her piggyback rides and talking about dolls.

Authorities say that after Chapman had gone home, McCullough dragged the little girl into an alley, choked her with a wire, then stabbed her in the throat and chest.

Prosecutors said that to conceal the body, he dragged it through a window at his home, then later loaded in into a car and drove to a wooded area. The search for the girl ended when her decomposed body was found 120 miles from her hometown.

In the 1950s, McCullough was a suspect with more than 100 others, but he told investigators he had been traveling to Chicago to get a medical exam before joining the Air Force. He settled in Seattle, working as a Washington state police officer.

The residents of Sycamore, a town 60 miles west of Chicago, eventually assumed the killer must have been someone just passing through the community.

However in 1994, McCullough's mother, Eileen Tessier, revealed on her deathbed that she had lied to police in 1957 to support her son's alibi. McCullough's half-sister passed the accusation on police in 2008.

"She knew what she did and she didn't want to die with that on her conscience," said prosecutor Julie Trevartchen on Friday.

McCullough's girlfriend in the 1950s also contacted police with evidence saying she had found his unused train ticket from Rockford to Chicago for the day Maria disappeared.

DeKalb County State's Attorney Clay Campbell said he was shocked when investigators told him they had a suspect in a 1957 murder. "When they said 1957, I said, you mean 1977? 1997?" he said.

On July 1, 2011, McCullough was arrested in Washington state at a retirement home where he worked as a security guard.

Authorities felt confident they had the right suspect was that Chapman picked out McCullough as the boy who identified himself as "Johnny" while the girls were playing.

Charles Ridulph, Maria's brother said he was relieved by the verdict.

"I feel totally spent, exhausted," he said. "I am not pleased with the new thoughts that I will have (about Maria's death). Some things I wish I did not know."

The half dozen relatives of McCullough present at the trial all said they wanted a guilty verdict.

Members of both families embraced one other after McCullough was led away in handcuffs. He will face sentencing later this year, where he faces the possibility of life behind bars.