The arrest of a suspect for the Claremont serial killings has been the highlight of outgoing WA Police Commissioner Karl O'Callaghan's career.

The low point was when his son Russell was injured in a methamphetamine drug lab explosion.

The 61-year-old commissioner, who was born in north London in 1956 before moving to Perth as a teenager in the 1970s, will officially retire as commissioner in two weeks after 13 years in the top job.

He joined the police force as a 17-year-old cadet, graduating as dux of his class.

He later became the first police officer in the state's history to complete a PhD.

He told ABC Radio Perth the role had been stressful but rewarding, and he never expected the job would carry such a high profile when he was first appointed to the position in 2004.

"I often say that apart from the Premier of Western Australia, probably the Police Commissioner is in the news more than anybody else," he said.

"The scrutiny is enormously high."

'A very difficult decision' for a father

Commissioner O'Callaghan conceded that scrutiny reached an all-time high when his adult son was arrested after being involved in a methamphetamine drug lab explosion in 2011.

"The most terrible thing was that he was most seriously burned and was taken straight to the burns unit at Royal Perth Hospital," he said.

"I couldn't go and see him because the problem I had was that if I had gone in to see him, just to hold his hand, there would have been some accusation that I had briefed him about what he should say to detectives or how he should approach the investigation.

"I actually drove to RPH in my own car and sat outside for half an hour, debating on whether I should go in and provide support that a normal father would provide, and I drove away.

"I did go and see him at the end of the next day after the detectives had been to see him, which I felt free to do then, but it was a very difficult decision as a father to do that."

Commissioner O'Callaghan said it was a few years later that he decided his 13 years in the top job would be long enough — if not too long.

"The last contract I signed was two years ago and I said at this point this should be my last contract because it does have an impact on family and an impact on things you might want to do apart from the police force." he said.

"And I think in organisations like policing it's good to have renewal and it's unusual for a police commissioner anywhere in Australia, let alone West Australia, to go for 13 years."

Commissioner O'Callaghan said it would be a relief not to be "on-duty" 24 hours a day, seven days a week and he leaves without too many regrets, but will miss the the "human aspect of policing" and the colleagues he has spent a large part of his life helping develop for senior roles.

The Police Commissioner with Perth school children. ( ABC News: Andrew O'Connor )

Reflecting on his career he said he was appointed commissioner at a difficult time in the state's history with the Kennedy Royal Commission into corrupt or criminal conduct by Western Australian Police Officers releasing its final report.

"So there was a whole lot of things going on about police corruption and police misconduct over a number of years and generally I think the confidence in policing was low and I very much saw my role as rebuilding that but I didn't ever think it was going to be 13 years," he said.

He believed his greatest strength in the job was looking outside the force for solutions to problems, and his decision to focus on what was driving the crime rate in the state.

He said one of his weaknesses, which was exploited by his competitors for the top job, was that he rose to the top job after serving as a traffic policeman and inside the police internal affairs unit

He admits there was a lot of noses put out of joint at the time with many senior officers questioning his ability for the job.

"There was a lot of that and 'this bloke won't last five minutes'," he said.

He believed his legacy would be making the police force "more 21st century" and helping it became more professional with a better understanding of what drives crime.

Claremont serial killings breakthrough

Commissioner O'Callaghan said he was always confident there would be a breakthrough in the Claremont serial killings before he retired.

"Bringing that to ... at least a partial conclusion [the suspect is yet to be tried] I think probably bought enormous confidence from the community that the West Australian police are equipped to do this," he said.

The deaths of three women over 14 months between 1996 and 1997 were dubbed the Claremont serial killings and sparked Australia's longest-running and most expensive police investigation.

Late last year a man was charged over two of those deaths.

Commissioner O'Callaghan said technological advances in DNA evidence in the past five to 10 years had made it possible for police to solve a lot of cold cases.

He said one of his biggest criticisms was the state's lack of investment in pathology and DNA testing to bring Western Australia up to world standards.

He said the Government needed to be pressured into improving forensic science for police in coming years, but that was a job for his successor.

He also identified the high rate of Aboriginal incarceration and the drug problem, particularly the use of methylamphetamine, or ice, as two of the biggest problems facing the state.