Jack Daniel McCullough, 72, of Seattle who then used the name John Tessier, was questioned after Maria Ridulph disappeared in 1957, the Chicago Sun-Times reported. At the time, he had what appeared to be an alibi, but investigators said they were able to break it in 2009.
Maria vanished while playing outside her house in Sycamore, Ill. Her brother, Charles, testified Monday that his sister's friend, Kathy Sigman, came to the door and told him Maria was gone when she returned to the street after a brief trip to her own house to get her mittens.
Sigman, who said Maria was with a man when she left, is expected to be the key prosecution witness.
Maria's body was found five months later dumped in a rural area with stab wounds in her throat.
Judge James Hallock is hearing the case without a jury.
"This ordinary night would end in horror," State's Attorney Clay Campbell said in his opening statement. "It would end with this defendant dumping her body in the cold, dark woods like a piece of garbage."
McCullough was acquitted earlier this year of sexually assaulting a woman relative in 1962. His lawyers said there is no evidence linking him to Maria's death.