VANCOUVER, B.C. - Adam Smolcic is hoping a professional data-recovery expert will prove his allegation that a police officer erased his cellphone video recording of Vancouver police shooting a knife-wielding man.

A civil liberties advocate says if true, it echoes other incidents where supposed video evidence of potential police misconduct went missing.

But Vancouver police say security cameras also recorded the confrontation and that will be vital evidence in the investigation of the shooting by the police department from the nearby city Abbotsford, B.C.

Smolcic, an unemployed marijuana activist, claims his video will show police didn't need to shoot Michael Vann Hubbard, who they suspected was breaking into parked cars last Friday.

"It didn't appear to me like this gentleman was a threat, even though he did apparently have an X-Acto knife," said Smolcic, 25, who estimates Hubbard was two or three metres away from the officers when he was shot.

"I don't believe that he advanced towards the officers, I don't believe their lives were in jeopardy and I don't believe the use of deadly force was justified."

But police, who identified the 58-year-old homeless man on Monday, contend Hubbard was advancing on the two officers brandishing the small knife and ignoring commands to drop it when he was killed. An autopsy concluded he died from a single gunshot wound.

Smolcic claims he captured almost the entire incident on four or five minutes of video with his mobile phone from across the street, 15 to 20 metres away.

Smolcic, who said has a federal licence to use medical marijuana for chronic pain, conceded he had "medicated" shortly before coming upon the street drama. But he's sure he properly activated the phone's video recorder.

He said he voluntarily turned the phone over to one of the officers who arrived after the shooting.

"When the police take your phone you assume you're not getting it back because it's evidence," said Smolcic.

"When he gave it back to me I totally thought I had lucked out and I've got this awesome video, and when I saw it was gone I was shocked."

Smolcic turned up Monday at the suburban office of Sherlock Forensics, which often works on data-recovery problems in legal cases.

Sherlock general manager John Anderson said if the video was ever there, he's confident the firm can recover it without disturbing the original file by copying everything in the phone's memory.

"Anything that's been on here as far as like calls being made, text messages being sent, videos being recorded, including deleted files also," he said.

Anderson, whose firm has worked to recover deleted child-porn images, said the delete function does not erase the whole file. It only removes the tag that identifies its location in the memory and frees the memory for reuse.

The recording would only disappear if it's then overwritten by another file, he said.

David Eby of the B.C. Civil Liberties Association said he sees parallels with similar police-related deaths, including the infamous Robert Dziekanski case, how the subject of a public inquiry.

The Polish immigrant died after being stunned repeatedly with a Taser by the RCMP responding to reports of an unruly man at Vancouver International Airport in 2007.

The inquiry was spurred by an uproar after a video shot by another traveller appeared to contradict the Mounties' initial depiction of what happened.

Eby said there have been other examples where police video was unavailable or not working at crucial moments.

Abbotsford police spokesman Const. Casey Vinet said his department is aware of Smolcic's allegation.

"I can tell you all aspects of what happened will be thoroughly examined and we want to speak with everyone who has any information," he said.

If Smolcic's allegation proved true, Eby said the officer who deleted the video would probably face criminal charges.

But it may not be the only record of the shooting. Vancouver police said Monday investigators were reviewing security camera recordings of the incident from two separate sources.

Police also interviewed about 50 other people in connection to the investigation.

Investigation of the shooting has been turned over to Insp. Len Goerke, head of Abbotsford's major crime section.

Vinet said the purpose of the investigation is to determine if any offences were committed under the Criminal Code or the Police Act.

But while Goerke is heading the investigation, Vinet said Vancouver police homicide detectives will be doing the legwork.

"We're confident the findings will be reached in a fair and objective manner," Vinet said.

The Office of the Police Complaint Commissioner of British Columbia will be providing civilian oversight of the investigation, he added.