Testing has ruled out a knife purportedly found at the former home of O.J. Simpson as having been used in the 1994 murders he was acquitted of committing in the "Trial of the Century," a Los Angeles Police Department spokesman says.

Forensic investigators conducted DNA and other tests on the blade after it was turned over to Los Angeles police within the last few months by a retired LAPD motorcycle officer.

The retired officer told investigators he had been given the knife by a construction worker, who in turn claimed to have found it on Simpson's property in the Brentwood neighbourhood of Los Angeles when the house was being torn down in 1998.

"We don't know if it's a hoax, but there's no nexus to the murders, based on the testing we've done," LAPD Capt. Andrew Neiman said in an interview Friday.

Police have declined to elaborate on the timeline of when the knife was recovered and turned over to investigators, but Neiman said in April it was possible "the whole story is bogus from the get-go."

A lawyer for retired Officer George Maycott has said the construction worker gave his client the knife after meeting him on a film set where the officer was providing security.

Attorney Trent Copeland said his client, who by then had retired, attempted to hand the knife over to the LAPD, but he was told there was no need because Simpson had been acquitted.

Simpson's former wife, Nicole Brown Simpson, and her friend Ronald Goldman were stabbed to death on June 12, 1994, at her condominium a few kilometres away.

The murder weapon has never been recovered. The sensational trial of Simpson, a former football star, was carried live on major television networks in the United States and transfixed much of the country.

Authorities have not described the knife, but the celebrity website TMZ reported it was a kind of folding knife typically used in hunting and fishing.

A medical examiner testified for the prosecution during the trial that Brown Simpson and Goldman were likely slain with a single-bladed, 6-inch knife.

Simpson was found liable for the deaths of Brown Simpson and Goldman by a civil court jury in 1997 and ordered to pay $33.5 million in damages to the victims' families, a judgment that has remained largely unfulfilled.

He was convicted in Las Vegas in 2008 of kidnapping and robbery in a bungled attempt to recover memorabilia from his storied football career. He is serving a prison term of up to 33 years.

Reports about the knife surfaced just as a popular new FX cable television drama series, The People v. O.J. Simpson, chronicling the trial, is airing.