Here Are Theories About the Knife That Was Used to Kill Nicole Brown and Ronald Goldman

What happened to the knife used to kill Nicole Brown and Ronald Goldman has become the stuff of lore.

The knife used to kill Nicole Brown and her friend, Ronald Goldman, was never produced as evidence in O.J. Simpson's infamous double-murder trial.

What happened to the weapon became a mystery of mythical proportions, with speculation and conspiracy theories rivaling those surrounding Lee Harvey Oswald and the assassination of John F. Kennedy.

Read: O.J. Simpson's Trial: Where Are They Now?

The stories have swirled for two decades and on Friday the riddle raged anew with the Los Angeles Police Department announcement that it was testing a blade found on the perimeter of Simpson's former mansion that had somehow been in the possession of a former cop for several years.

The knife's twisted tale began when prosecutors discovered Simpson had purchased a 15-inch collector's knife weeks before his ex-wife and Goldman were viciously stabbed to death in the cramped courtyard of Brown's Los Angeles condo in June 1994.

Police had entertained several scenarios about the murder weapon - that it was flushed down a jetliner toilet by Simpson as he flew to Chicago on the night of the murders; that it was dumped into a trash bin at O'Hare International Airport and that it was secreted inside Simpson's hanging travel bag, which he turned over to defense attorney Robert Kardashian upon his return from Chicago.

Supermarket tabloids had a field day with the blade, speculating it was being hidden by Simpson supporters, and most recently in 2012 that Simpson planned to auction it for $5 million.

Read: From the Gloves to the Bloodied Clothes, What Happened to Evidence in O.J. Simpson's Trial?

In Simpson's preliminary hearing, prosecutors put Ross Cutlery employee Jose Camacho on the stand, who testifed he sold the knife with a six-inch retractable blade to Simpson in May 1994.

"I guess something attracted him about the knife. It's a nice-looking knife. And he just, he liked it," Camacho told the court.

But the knife was missing, defense lawyers said. It reappeared later during the trial when Simpson's "Dream Team" turned over a manila "mystery envelope" with the knife inside.

Testing revealed there was not a mark or piece of forensic evidence on it, and it was never introduced at trial by the prosecution. Jurors never heard Camacho testify because prosecutors refused to call him to the stand because he had been paid for a tabloid interview. 

Some pundits speculated that if the murder weapon, like Brown's blood-stained dog, could talk, the case would have been quickly solved.

It was wielded in a frenzy, according to autopsy reports. Goldman was stabbed more than 20 times, and bled to death where he fell. Brown was also knifed several times, but it was a gaping slash across her neck that knicked her backbone and nearly decapitated her that ultimately killed her, the Los Angeles County Coroner's office ruled.

On Friday, police said they were trying to determine why an unnamed retired officer kept the knife handed to him by a construction worker at Simpson's former Brentwood home, which was razed in 1998.

That officer reportedly was off-duty at the time and was moonlighting as a security officer for a film location shoot across the street. He allegedly recently contacted an acquaintance in the department's elite Robbery-Homicide Division, saying he wanted to frame the knife and wanted case file information to engrave on the wall hanging.

The acquaintance allegedly told superiors, who confiscated the blade.

Simpson, who was acquitted in 1995, cannot be retried for the killings.

Watch: Man Who Owns O.J. Simpson's White Bronco: I've Been Offered $300,000 For It