An American martial arts expert found guilty of strangling a renowned former North-East scientist will spend 15 years to life in prison for the 1995 murder, a court ruled yesterday.

Paul Cain, 28, was sentenced in San Diego after being convicted in May of second-degree murder for killing 73-year-old geophysicist Professor Stanley Runcorn, formerly of Newcastle University.

Cain, a black belt in karate and competitive kickboxer, did not deny that he beat and strangled Prof Runcorn.

He claimed, however, that he flew into an uncontrollable rage when Prof Runcorn pushed him down on a hotel room bed in an aggressive sexual advance that reminded Cain of being molested when he was a child.

Howell said the judge denied his motion for a new trial. Cain intends to appeal against conviction.

Prof Runcorn, a visiting professor at the University of Alaska at the time of his death, once headed the physics department at Newcastle University and served as an advisor to the Pope.