Christopher Dorner: Police officers who kill

Photos of Christopher Dorner
Image caption Photos of Christopher Dorner provided by the Los Angeles Police Department

Christopher Dorner used his law enforcement training to target other police officers. What makes cops turn criminal?

The manhunt for former fugitive killer Christopher Dorner has finally come to an end more than a week after he allegedly shot dead two civilians in Los Angeles.

But Dorner - accused of killing three people - wasn't just a criminal. He was also a former police officer.

He claims he was fired without just reason in 2007, and vowed to use all of his police and military training to bring "warfare" to the Los Angeles Police Department (LAPD).

He is one of an extreme minority of officers that cross the line from cop to criminal.

"The vast majority of officers maintain a good ethical condition," says Jack Digliani, a police psychologist with the Loveland, Colorado Police Department.

"We serve and protect, and many officers complete a career without these kinds of incidents."

While most police officers do not have criminal inclinations, a surprising number of criminals have aspired to be police officers.

Alexandria-based clinical psychologist Stanton Stamenow interviewed numerous men he described as "hard core criminals", for a study he helped conduct in the 1970s. One question he posed was what they had wanted to be as children.

"A significant number replied they wanted to be in law enforcement - a policeman, an FBI agent, in some cases the military," he says.

"It was about power and control for the sake of power and control."

And while police forces do extensive testing to weed out those who are unstable, the police officers who do end up committing criminal activity often fit this description.

"If you get a cop who is a criminal, then you may get someone who uses the badge to intimidate, or use excessive force," says Stamenow, author of Inside the Criminal Mind.

These men, he says, were fixated on the trappings of power - a gun, a cruiser, a uniform - and the accompanying authority.

"The authority and power that comes with this position is not enough for this sort of person, who wants to show that he is special, he is unique, he can go beyond."

That sounds like a fitting description for Drew Peterson, the Chicago police officer convicted of murdering his third wife - a case that only took off after his fourth wife disappeared.

But even amid the media scrutiny, he made himself available for interviews and publicity appearances, including one that tried to set him up with a new wife.

"This kind of person crosses lines," says Stamenow, who notes he has never personally treated Peterson. "Maybe they do well at work, but they have troubled interpersonal relationships. Women are their hostages and their slaves."

When people acquire power, they have the opportunity to abuse it, notes Michael J Perotti, a clinical and forensic psychologist in Loma Linda, California. This happens in the police, as in other walks of life.

"There's sexual assaults by police out there with people, there's drug trafficking," he says. "Like any profession, there are certain places where police can get out of control."

There are multiple cases where police officers have committed rape and sexual assault: Michael Pena, was an off-duty police officer when he brutally attacked a stranger in a New York City alley while brandishing his police gun. He is now serving 85 years for rape and sexual assault. A police officer in Houston was recently sentenced to life in prison for raping a waitress while on duty.

When current officers do break the law, they have more access to weapons and other tools than those in other professions. Take the case of Gilberto Valle III, a six-year veteran of the NYPD. Police allege that Valle had been bartering with a New Jersey man to buy a woman he could then cook and eat, and that he misused his access to police databases to stalk potential victims.

Image caption London serial killer Dennis Nilsen had served on the Metropolitan Police

Valle has been charged with conspiracy to commit kidnapping and accessing unauthorised data from the National Crime Information Center. He has pleaded not guilty.

Dorner was particularly dangerous because his military and police training made him an expert marksman.

But of course, you don't need police training to be a dangerous criminal.

Serial killer Dennis Nilsen murdered and dismembered at least 15 men during a five year period in London.

And though he served an eight-month stint as a member of the Metropolitan Police, it was his training as a cook - and his deftness with a knife - that best helped him conceal his crimes.