The boys, who were both 14 at the time, denied the attack but were found guilty by a jury at Hull Crown Court after seven hours of deliberations.

The BBC's Richard Wells: "A ferocious and unprovoked attack"

Judge Arthur Myerson QC, who described the case as a "particularly difficult one", adjourned sentencing pending probation and psychiatric reports.

But both boys, who cannot be named for legal reasons, were remanded in secure accommodation and warned that custodial sentences were bound to follow.

Stabbed in the cheek

Andrew Robertson QC, prosecuting, said the attack happened at a beauty spot near Harrogate, North Yorkshire, in January this year.

He told the court that the boys, one of whom is now 15, watched the film at the house of a local man Paul Aurens, a convicted drug dealer who admitted an interest in Satanism and witchcraft.

One of the attackers was said to have taken cocaine at the man's flat before the pair lured their 13-year-old friend to the Birk Crag area.

One of the boys then suddenly produced a knife and rammed it into his head.

When he tried to get away, said Mr Robertson, the second boy stopped him and the first boy continued stabbing his cheek, head and body. The attack only stopped when the victim pretended to be dead.

Planned in advance

The victim was found by chance 40 hours later by an elderly man out walking his dog.

In hospital, a surgeon found he had suffered 11 stab wounds to his head, three of which had gone through the skull.

The injured boy, now 14, suffered a fractured rib, collapsed lung and temporary paralysis on his left side.

Mr Robertson said the two boys had planned the attack in advance and had even brought along a bin bag in which to hide the body.

"It was by good chance and good fortune that he was eventually found," he said.

Jury watches the film

During the two-week trial, the seven-man, five-woman jury spent two hours watching Scream on televisions specially brought into court.

The film, which stars Friends actress Courtney Cox, features a group of college students being stabbed by killers who turn out to be their classmates.

On a video played to the jury, the victim told police he thought his two friends might have been influenced by the movie.

Mr Robertson accused the two boys of being obsessed with the film and with knives.

He said the boys had drawn pictures of the lock knife used to stab their friend in an exercise book and had also drawn masks similar to those worn by the killers in the film.