Luke Walmsley was stabbed through the heart

Luke Walmsley, 14, was knifed through the heart at Birkbeck Secondary School in North Somercotes, Lincolnshire, in November 2003.

His parents watched tearfully as Nottingham Crown Court was shown footage of him with a bloody chest.

A 16-year-old boy, who cannot be named, has denied a charge of murdering Luke.

Boy threatened

Yvonne Coen, QC, prosecuting, told the court the pair disliked each other, but it was unclear what had motivated the stabbing.

She said the defendant had told police that Luke had said he could beat him up.

The court was told defendant held the blade against another boy's throat on the morning of the killing.

Later, he was seen standing outside the class where the victim was finishing a lesson, twiddling the knife in his fingers.

Ms Coen said that as Luke walked past to go to his next lesson, the defendant stepped forward "and without a word stabbed Luke in the chest".

'Considerable force'

A subsequent post mortem examination revealed he suffered a single stab wound to the heart.

The jury heard the wound was 4.3 inches deep and the knife had been inserted with "considerable force" at least as far as the hilt.

The court was shown CCTV footage of him with blood on his chest just before he collapsed.

When the defendant was charged with murder, Ms Coen told the court, he said: "I did not intend to kill him."

She said several pupils, who were expected to give evidence via video link during the trial, reported hearing the defendant threaten to kill Luke on a number of previous occasions but had not taken him seriously.