David Copperfield was forced to break the magicians code in court Tuesday, when a judge ordered him to explain one of his most famous tricks following a lawsuit from an injured participant. British tourist Gavin Cox, 58, is suing the illusionist for negligence after he claimed he was injured after taking part in Copperfield’s “Lucky #13” trick in Las Vegas in 2013, the BBC reports. Cox said he has suffered chronic pain and brain injury following a fall that dislocated his shoulder.