Phoenix Fox 10 anchor John Hook had hoped to finally crack the case after he re-investigated it and got authorities to allow him to retest DNA samples found on a suspect's car.
The big reveal came in a live segment Monday night before a panel of people that included Crane's son, the prosecutor in the case, the jury foreman and the defense attorney for John Henry Carpenter -- the man who was eventually acquitted of murder in the case.
"The DNA found on the door of John Carpenter's rental car is not, is not from Bob Crane," Hook said. "The tests actually picked up two DNA profiles. A major contributor is from a man, his identity is unknown. Second DNA profile is a partial profile too degraded to reach any conclusions."
Crane's son, Robert Crane Jr., mouthed "wow" as the results were read.
"I'm shocked right now," he said. "There were always two people in my mind: John Carpenter and my stepmother, for different reasons. But it was on John's car."
Crane, who played the beloved Col. Hogan in the popular television series, was found bludgeoned to death in his Scottsdale, Arizona, apartment in 1978.
The case captured headlines as it came along with revelations regarding Crane and his sex life, which included videotaping and photographing his sexual encounters with women.
His friend, Carpenter, was pegged early on as a person of interest and in 1994 was put on trial for the murder after the case was reopened.
Carpenter was eventually acquitted and died in 1998. The case was dramatized in the 2002 film "Auto Focus" starring Greg Kinnear and Willem Dafoe.
With improved DNA testing methods, Hook had hoped that blood found on Carpenter's rental car would offer some answers.
Carpenter's defense attorney Steve Avilla had always maintained his client's innocence.
"This is wonderful news for his family," Avilla said Monday. "This is wonderful news for John who has passed away to know that he has finally been vindicated. Not only in a court of law, but in a court of public opinion."