Discuss as:

72-year-old ex-cop convicted of slaying Illinois girl in 1957

For decades, the murder of Maria Ridulph remained unsolved until the prime suspect's alibi fell apart a half century later. On Friday, Jack McCullough's trial came to an end when a judge found him guilty of murder. NBC's Kevin Tibbles reports.

Nearly 55 years after the remains of 7-year-old Maria Ridulph were found in Illinois, Jack Daniel McCullough, 72, was convicted Friday for the girl's kidnap and murder.

The trial of the former Washington state police officer in Dekalb County, Ill., is believed to be one of the oldest cold case murder prosecutions in U.S. history.

McCullough now faces life in prison when he is sentenced later this year.

His half-sister, Janet Tessier, said she was elated he was found guilty.

“He’s an evil son of a bitch, and he’s right where he’s supposed to be,” Tessier told the Chicago Sun-Times, who testified that McCullough’s guilt-ridden mother admitted on her deathbed that she knew her son was involved.

DeKalb County Sheriff's Dept. via AP, file

Jack McCullough, of Seattle, is seen in a mug shot taken July 28, 2011.

In 1957, the case unsettled parents across the nation, and even then-President Dwight Eisenhower asked to be kept up to date.

Prosecutors said McCullough kidnapped Ridulph while she played with a friend, Kathy Chapman, near their homes in Sycamore, Ill., about 60 miles west of Chicago.

McCullough pleaded not guilty in the case. He waived his right to a jury trial and opted for a bench trial instead that lasted a week. He declined to testify. Following four days of testimony examining the slaying of Ridulph, prosecutors and defense attorneys in the case rested on Thursday, and Judge James Hallock heard closing arguments on Friday.

When the incident happened, Chapman told police that she and Ridulph were approached by a man in his early 20s wearing a multi-colored sweater who identified himself as “Johnny,” according to court documents. Later, Chapman said she went inside her home to get mittens and when she returned, Ridulph and “Johnny” were gone.

Stay informed with the latest headlines; sign up for our newsletter

McCullough was 17 at the time of the killing and lived a few blocks away from the Ridulph family. He denied any involvement in the case.

A massive search to find Ridulph was launched by the FBI and in April 1958, investigators found the girl’s skeletal remains in a forest some 120 miles away from her home.  

McCullough, who then went by John Tessier, was on an early list of suspects in 1957, but he claimed that on the day Ridulph was kidnapped, he had traveled to Chicago to get a medical exam before enlisting in the Air Force.

The FBI said the case went cold after McCullough joined the military and legally changed his name to Jack Daniel McCullough.

Watch the most-viewed videos on NBCNews.com

Investigators reopened the case a few years ago after McCullough’s former girlfriend told them she found his unused train ticket from Rockford to Chicago on the day Ridulph vanished. He was arrested on July 1, 2011 at a his home in Washington state where he worked as a security guard. A judge set his bail at $3 million and police kept him in custody until he would return to Illinois to be prosecuted.

The Associated Press contributed to this report.

More content from NBCNews.com:

Follow US News from NBCNews.com on Twitter and Facebook