SYCAMORE -- Over the years, evidence goes missing or passes through so many hands it's rendered useless. Murder weapons disappear, and witnesses' memories dim or are carried to the grave.
Those are obstacles that have persistently stymied prosecutors trying to crack decades-old cold cases -- and that now await authorities building a case against a former Washington state police officer in the 1957 slaying of a 7-year-old girl in this northern Illinois farming community.
Can the little girl's friend, now in her 60s, remember with certainty what the suspect looked like? Will an unused train ticket, discovered half a century later, undermine Jack Daniel McCullough's alibi that he was in Chicago having a military medical exam the day that Maria Ridulph disappeared?
"Proving guilt beyond a reasonable doubt in court-- that'll be very hard," Patrick Solar, a Sycamore police detective who spent years investigating the killing before he retired in 2002, said Wednesday. "I don't envy them having to do it."
Ridulph's abduction in the winter of 1957 captured the nation's attention, and President Dwight Eisenhower and FBI Director J. Edgar Hoover asked to be kept up-to-date about the massive search. Her body wasn't found until spring, by which time it was so badly decomposed a cause of death couldn't be determined.
Clay Campbell, the chief prosecutor in Illinois' DeKalb County, won't discuss what evidence led authorities to arrest McCullough this month in the Ridulph case, one of the oldest cold-case investigations to become active again. He is seeking the suspect's extradition from Seattle to stand trial for the little girl's slaying.
"I am well aware of the precarious nature of prosecuting a case you cannot prove," Campbell said at a news conference Tuesday. "But we are confident that Mr. McCullough killed Maria Ridulph."
Authorities in the '50s seemed befuddled from the start, said Solar, who went through Ridulph's file off and on starting in the 1980s. The initial investigators listed more than 100 suspects -- a sign they were never hot on anyone's trial.
Among the many theories they floated then discarded was that an organized crime group may have kidnapped the girl for ransom money, Solar said, citing the files.
The friend of Maria's, Kathy Sigman, told authorities a young man who called himself "Johnny" approached them while they were playing and offered to give them piggyback rides. She left to get mittens, and when she returned, her friend and the man were gone.
McCullough, whose name at the time was John Tessier, lived nearby and was on an early list of suspects. But he had an alibi. He told authorities he was in Chicago that day getting a medical examination before enlisting in the Air Force. He later moved out of the area, served in the armed forces and ultimately worked as a police officer in Washington and then a security guard at a retirement home -- where he was arrested July 1.
Physical evidence is unlikely to play any role at a trial, Solar said. As part of his investigation, he sought out clothes found on Ridulph's dead body, samples of her hair and a doll that files indicated were recovered from the crime scene. But he was told they couldn't be located.
A verdict, instead, is likely to hinge on memories.
Investigators reopened the case three years ago, after McCullough's girlfriend from 1957 told them she found his unused train ticket from Rockford to Chicago from Dec. 3, 1957, the day Maria vanished. Sigman, who is now Kathy Chapman, identified McCullough recently through a photograph of Tessier from the 1950s, which she said she was never asked to do half a century earlier.
McCullough told The Associated Press in a recent jailhouse interview that he didn't use the train ticket because his stepfather gave him a ride to Chicago. And he said his "iron-clad alibi" would be supported by military records of the medical exam -- except that officials at the St. Louis records repository confirmed Tuesday to the AP that his file had been destroyed in a 1973 fire.
With more than 200,000 unsolved killings since 1960, according to the FBI, cold cases have become a bigger part of prosecutors' jobs nationwide.
In many cases, DNA evidence has opened the door to renewed prosecutions. With missing physical evidence, Solar says there's little chance DNA factors into the Ridulph case.
Rochester, New York-based district attorney Sandra Doorley knows the challenges better than most, with several cold-case convictions to her name, as well as a recent defeat.
She looked on as jurors this year acquitted Willie James Kimble, 78, of sexually assaulting and bludgeoning to death a blind homemaker, Annie Mae Cray, in 1972. Among the vital evidence that had gone missing was the alleged murder weapon, a bloodied log.
In rare cases, the passage of time can help prosecutors.
In a 1955 case of three slain Chicago boys, witnesses refused to tell authorities for decades how Kenneth Hansen told them he'd raped young boys and warned if they said anything they'd "end up" like the boys.
"After time and distance, they came forward because they knew he could not hurt them anymore," said Jennifer Coleman, a Cook County prosecutor who won a conviction in the 2002 murder retrial of Hansen.
Well-organized interview notes and crime scene reports can also be crucial in convincing jurors evidence is sound. The span of five decades in the Ridulph case makes that a challenge.
By the '80s, the Ridulph files were in disarray, some kept by the FBI and some by Illinois State Police, Solar said. Determined to put them in order in one location, he got the agencies to send him what they had, then organized it all in two boxes and stored them in Sycamore.
Despite the hurdles to successfully prosecuting such an old cold-case, Solar said a conviction was possible.
"It has been done," he said. "It can be done."