New research in the United States says many fatal shootings by the police are the result of individuals provoking officers to kill them because they want to die.

The phenomenon is known in the US as 'suicide by cop'.

The study shows that, last year, one in six of all police shootings were the result of people stage-managing their own deaths.

In one case, two members of a religious cult hijacked a bus because they wanted to confront armed police and force officers to kill them.

In another, a youth in New York provoked an officer to kill him.A correspondent for the BBC in Los Angeles says the effect on police officers of killing someone in such circumstances can be devastating.

He says officers in the city are being trained to deal with suicidal suspects.