The confessed "Yorkshire Ripper" is a paranoid schizophrenic who believed he was on a divine mission to kill prostitutes, England's chief prosecutor told an Old Bailey murder trial yesterday.

But although the psychiatrists who examined Peter Sutcliffe all agreed the bearded 34-year-old truck driver was temporarily insane when he killed 13 women in five years, it will be a jury, not the doctors, who must decide Sutcliffe's state of mind, said the attorney general, Sir Michael Havers.

Havers told a six-woman, six-man jury there might be "substantial conflict between what Sutcliffe told the police and what he told the doctors. There are no outside facts on which they [the doctors] can rely. They might be wrong," he said.

Sutcliffe pleaded not guilty to the murders but guilty to manslaughter with "diiminished responsibility" or insanity. The jury will decide which of the two pleas to accept.

Havers said at one point Sutcliffe told doctors he was on a "divine mission" from God to kill prostitutes.

He said Sutcliffe viciously attacked his victims with various weapons and left the bodies partly naked. He quoted Sutcliffe as saying he did this "so that when they are found they would look as cheap as they were."

Havers said some of the 13 victims, whose ages ranged from 16 to 47, were prostitutes. But the last six attacks from 1979 to 1980 were against women who were not prostitutes.