A judge's decision to allow a prosecutor to give a closing speech in a case against an alleged drug trafficker who was not legally represented was a "material irregularity", the Court of Appeal has ruled. Explaining why it quashed a 10-year jail term for Chan Hoi-wing and ordered a retrial, the panel of three judges said Madam Justice Maggie Poon Man-kay also erred in allowing the Court of First Instance jury to be told Chan's co-defendant had pleaded guilty to a drugs charge. Chan was convicted of trafficking in various dangerous drugs including heroin and the methamphetamine Ice. She sought leave to appeal after the conviction in January. The ruling centred on the fact a lawyer would typically be better able to convince a jury than an unrepresented defendant. In the judgment, vice-president of the Court of Appeal Mr Justice Michael Lunn wrote: "We are satisfied that the fact that counsel for the prosecution was permitted to make a closing speech to the jury in this case was a material irregularity." Citing precedent from previous cases, he added: "When the outcome of a case hinges on findings of fact … the advocate will undoubtedly play a highly influential role in the verdict to be returned by the jury." Lunn said the decision to make the co-defendant's guilty plea known would create an "obvious potential prejudicial effect" on Chan as she was the only other person found at the premises at the time of the offences in October 2012. He said the trial judge had a duty to Chan to consider whether the matter of the guilty plea should be placed before the jury. "Her failure to do so was a material irregularity," Lunn wrote.