Jamie Petrolini, 19, could not explain why, after the killing, he put on the dead man's glasses and spat fake blood on to the table of a burger bar.
Under cross-examination, Petrolini insisted that he had stabbed Mohammed el-Sayed to death because he believed it was an SAS initiation test and that Richard Elsey, 19, his co- accused, was an SAS officer. He denied that he took the lead in the killing and said he was following Elsey's orders.
Petrolini, of Grantown-on- Spey, Highland, and Elsey, of Beaconsfield, Buckinghamshire, both deny murdering Mr el-Sayed in London on January 14 this year. The prosecution alleges that they jumped into Mr el-Sayed's car when it stopped at a junction in Bayswater, west London, and that Petrolini slashed the man's throat and stabbed him to death while Elsey held him from behind.
Petrolini has admitted manslaughter on the grounds of diminished responsibility.
The trial continues today.