In a tortured two-page letter, Richard Elsey, 19, accused of restraining Mohammed El-Sayed while Jamie Petrolini, also 19, slit his throat and stabbed him to death, wrote: 'Nothing seems worth living for. I'm not a boy, I'm a machine that lives. No feelings.'
In the letter to Tina Duff, a fellow student at Modes Study Centre in Oxford, which was read in court, he said he had happy memories of being 'a child with his sister in a park, throwing snowballs, laughing, calling for help from mummy and daddy.
'But then I return and the memories with me, the violence, pain, the sister lying in the rain, blood everywhere, on my clothes, on the car on the road .
. . on my soul that is now in hell . . . I have become an animal, with only one thing on my mind to live and let die.'
Margaret Williams, another student at the crammer, said Mr Elsey told her that his sister died in a car accident.
Others who studied for A-levels with Mr Elsey and Mr Petrolini described their close relationship and obsession with the Army. Annie Jones said that she and friends met Mr Petrolini, a former pupil of Gordonstoun, one night marching down a street in Oxford with Mr Elsey right beside his face shouting 'Left, Right, Left, Right'. She said the latter was so serious he appeared not to see them.
Ms Duff said she saw Mr Petrolini running with a heavy rucksack apparently being trained for the paratroops by Mr Elsey, who claimed he was already a member. She described Mr Elsey as 'solemn and introverted' and as the more dominant of the two.
Barbara Pitman, Mr Petrolini's former landlady, described him as a nice young man but said that some people thought him a 'weirdo'. He embarrassed her by doing press-ups on the pavement.
The jury saw a security camera film of the friends posing as plain- clothes detectives at the Golden Horse Shoe Casino in Queensway, west London, last November. They were asked to leave by the manager who did not believe their story that they were police officers looking for youths preying on local businessmen. Mr El-Sayed gambled in the same casino on the night that he was murdered.
Mr El-Sayed was found slumped in his grey Audi car, soaked in blood, on 16 January this year. Dr Ian Hill, pathologist, said his throat had been cut twice and he had been stabbed 12 times in the chest and once on the arm.
David Calvert-Smith, for the prosecution, alleges that the students decided to murder Mr El- Sayed when they could not find a pimp or drug dealer. Mr Calvert- Smith said they might have committed the 'perfect crime' but Mr Petrolini could not keep quiet when they returned to college.
Mr Elsey, of Beaconsfield, Buckinghamshire, and Mr Petrolini, of Grantown-on-Spey, Highland, deny murder. Mr Elsey claims he thought Mr Petrolini was only going to rob Mr El- Sayed. Mr Petrolini has admitted the killing but denies murder on the grounds of diminished responsibility. He says he believed his friend was in the paratroops or Special Air Service and that the killing was an initiation test.