Former teacher David Arthur was yesterday found guilty of supplying P to four young people at a party at his home by a High Court jury in Auckland. Arthur's downfall was sealed when he videotaped the four smoking the drug in his bedroom last year. Two of the young people took the tape and gave it to Sunday Star-Times reporter Amie Richardson, who used it to form the basis of a front-page expose. One of the four was former paparazzi photographer Jonathan Marshall, an acquaintance of Richardson's. Arthur's defence suggested that he had been set up and sold out by Marshall, which was denied. Marshall, who once exposed celebrity secrets on a tabloid website for a living, received permission to have his face and voice disguised during TV coverage of the trial. Arthur will be sentenced next month. Justice John Preistly said imprisonment was "inevitable".