Colin James, 50, has been accused of murdering Mr Martin, an Australian-born millionaire, on 29 December last year even though the body has never been found.
The prosecution case opened during committal proceedings before a magistrate at High Wycombe, Buckinghamshire. Mr James, of north London, has not entered a plea.
The court heard that Mr Martin was killed in a garage workshop among vintage cars, and that the murderer had tried to clear up the blood, leaving footprints behind.
Roger Coventry, for the prosecution, said it might be suggested that Mr Martin was not dead. However, since his disappearance his bank account has not been touched and no contact has been made with family or friends.
The hearing was adjourned until today.