Police investigating a murder scene on December 10, 1945 found a chilling message scrawled on the wall in lipstick.
Chicago woman Frances Brown was found in her apartment stabbed and shot to death.
Written on the wall was the message: “For heaven’s sake catch me before I kill more, I cannot control myself.”
It came six months after another fatal stabbing of Chicago woman, Josephine Ross. Like the Brown case, nothing of value had been taken from the apartment.
William Heirens photographed behind bars. (Getty)
And in January 1946, a six-year-old girl was kidnapped and murdered.
All the cases were quickly linked to the one killer by police, though the connections were somewhat dubious.
After 370 suspects were questioned, some under torture, a 17-year-old was arrested for attempted burglary.
William Heirens was interrogated for six days, during which time he was beaten, starved and drugged.
When drugged, Heirens spoke of another boy named George Murman who committed the crimes.
William Heirens said he was pressured by his lawyers to plead guilty. (Getty)
After questioning his family and friends without success, police concluded George was an alter-ego Heirens had created for himself.
The alter-ego allowed Heirens to psychologically separate himself from the crimes he had committed, police hypothesised.
A partial fingerprint found at the scene of the Frances Brown murder also did not eliminate Heirens as a suspect.
But the print was so smudged that two-thirds of the population could have matched it.
Convinced of his guilt, Heirens’ defence lawyers offered to make a deal with prosecutors.
If he pleaded guilty, he would be spared the electric chair but face a life sentence.
Using details he had read in the Chicago Tribune, Heirens drafted a confession under the supervision of his lawyers.
Police ignored the 29 inconsistencies between his confession and the facts of the case.
“I confessed to save my life,” he later said.
William Heirens became the first prisoner in Illinois to earn a degree behind bars. (Illinois Department of Corrections)
After his sentencing, the local sheriff asked Heirens if the little girl he had pleaded guilty to killing, Suzanne Degnan, had suffered.
“I can’t tell you if she suffered, Sheriff Mulcahy. I didn’t kill her,” Heirens said.
“Tell Mr Degnan to please look after his other daughter, because whoever killed Suzanne is still out there.”
At the time of his death in 2012, Heirens was the longest-serving prisoner in Illinois history