(CNN) -- Investigators believe it is "highly, highly probable" that a now-dead murder convict was involved in the 1989 disappearance and presumed death of University of Florida student Tiffany Sessions, Alachua County Sheriff Sadie Darnell told reporters Thursday.
Darnell said numerous clues appear to link Paul Rowles, who died in prison after being convicted of a separate, 1992 murder, to Sessions' disappearance.
"What we now need is for you as media ... (to) study (the) timeline of Paul Rowles, get his face out there at different ages, study locations where he lived, worked," Darnell said. "Go back in time 25 years. ... If you had any involvement with him ... come forward."
No DNA evidence has linked Rowles to the Sessions case, Darnell said. But Darnell said other clues appear to link the pair, including: Rowles' criminal history; his presence in the Gainesville area at the time; and an entry on a calendar found in this prison cell -- the numbers 2-9-89, which matches with the day Sessions disappeared.
Authorities said Sessions, then 20, was reported missing after she didn't return from a run.