A MURDER conviction had to be quashed yesterday after a High Court judge got the law wrong. The judge, who departed from the standard direction judges should give the jury on the law, got a ticking off from the Court of Appeal. Mr Justice Sears, in giving the judgement of the court, said: ''Homemade directions may relieve the monotony of summings-up, but they are liable to lead to error, subsequent appeals and additional strain on court time.'' He said when provocation was raised as a defence, as in this case, the judge must give clear and succinct directions on the law to the jury. The court held that Mr Justice Gall seriously misdirected a jury trying a trainee fashion model for murdering a friend last September by saying they should convict of murder unless the defendant proved he was provoked. The Court of Appeal said the standard direction on the defence of provocation was easily understood - the prosecution had to prove the defendant was not provoked before he could be convicted of murder. The court, also comprising Mr Justice Macdougall and Mr Justice Nazareth, had allowed the appeal at an earlier hearing and was handing down reasons for judgement. It ordered a re-trial. Lai Hon-man, 21, had admitted killing Mr Shing Wai-keung, 19, but denied murder. On April 9, 1991, Lai stole Mr Shing's cash card and withdrew $9,000. The next day Mr Shing asked Lai to go to his flat and Lai deliberately took loud speaker wire with him. The two had a row and he tied up Mr Shing. Lai alleged that he lost control after being kicked and he pulled the wire around Mr Shing's neck during a struggle. On Mr Robert Forrest's second ground of appeal, that the judge failed to give the jury a direction that Lai had a clear record, the court agreed the judge must give the standard direction on good character. But it held that his failure to do so had not led to a miscarriage of justice. The court said it was the duty of prosecuting counsel to remind the judge of non-directions and to correct him on mis-directions; neither of which were done in this case.