Allen County Sheriffs Department John Miller after his arrest by police on July 15.
He is scheduled to appear in court on Monday.
Charges could be formally filed this week.
Tinsley was reported missing on April 1, 1988, when she didn't return home from visiting a friend in Fort Wayne. The family lived in the 300 block of West Williams Street. Her body was found dumped in a ditch three days later; she had been raped and strangled, reports CBS News' Don Dahler.
It took April Tinsley 10 minutes to die, he told investigators. The killer had left DNA evidence, but no match could be found.
The prosecutor's office said it won't release any more factual information about the case, based on the Indiana Rules of Professional Conduct for attorneys, the announcement said. He also kept haunting investigators for 30 years with taunting messages and clues claiming he murdered Tinsley and "would kill again". Check News-Sentinel.com early Tuesday afternoon for details. Until now, taunts comprised much of the evidence about Tinsley's killer.
In 1988, an 8-year-old girl, was raped and murdered after being abducted from her neighborhood in Fort Wayne, Indiana. This time, police found three used condoms in three different in towns with notes attached to them.
For years after the eight-year-old's body was found in 1988, Miller allegedly haunted the community by sending sickening notes to potential victims along with pornographic Polaroids and used condoms.
In May, a detective in the Fort Wayne Police Department sent the suspects DNA to Parabon NanoLabs, which works with law enforcement agencies to help identify possible suspects. Three used condoms that Miller allegedly discarded and were found among the pulled trash matched the genetic profile found on April and in the condoms left with the notes in 2004, police said. It was not until recently that the identity of the killer was discovered via matches in a genealogy database.
Miller allegedly admitted kidnapping Tinsley and then sexually assaulting and killing her at his Grabill home before dumping her body on April 2, 1988, according to the affidavit, which was filed Sunday.
The DNA technique used to catch him sees investigators cross-reference samples members of the public have uploaded to publicly-searchable websites.
Despite finding DNA evidence on April's underwear during the initial investigation, police failed to narrow down a suspect. After that early July development, police began surveillance on Miller's Grabill mobile home and began to analyze his trash.
Thanks to advancements in DNA technology, Miller's arrest has been part of a stream of cold case breakthroughs.
Miller told detectives he choked her to death so that she wouldn't report him to police.
The suspect told police he disposed of her body in a ditch the following day. As he drove past, he threw April's shoe out of his vehicle, he allegedly told police.