The Court of Appeal freed a man convicted of strangling his wife after finding the teenage son's eyewitness account of the killing was seriously flawed. Mr Justice Michael Stuart-Moore said yesterday the court carefully dissected the son's testimony in deciding to quash the manslaughter conviction of Ling Kam-wah, 39, who was found guilty of killing his wife, Ho Wai-chun, on February 1, 2000. He said the cornerstone of the prosecution's case was the testimony of the son, Ling Siu-tong, who was 15 at the time. Siu-tong told the trial his parents were arguing over money in the bedroom of their Mongkok flat before he saw his father strangle his mother, ransack the flat and flee. But Mr Justice Stuart-Moore said yesterday the number of conflicting statements in the boy's evidence made the conviction unsafe. He quashed the jury's verdict of guilty of manslaughter by provocation. Mr Ling, who pleaded not guilty to murder, had been jailed for 12 years. 'These [improbabilities concerning Siu-tong's account] have to be coupled with our concerns about Siu-tong's own veracity, making him, as the central pillar to this prosecution, an unsound foundation,' the judge said. 'Whether we look at the motive, the manner of the killing or the subsequent events as alleged against [Mr Ling] by [Siu-tong] none of this evidence hangs together comfortably or without question marks being raised.' Defence counsel Andrew Raffell told the court the boy had continued to change his story and lie up to the day he testified. Although Mr Raffell stopped short of describing the boy as the culprit, he told the court Siu-tong's web of lies could be seen as an attempt to divert attention away from his own movements. Siu-tong's sworn statement included an explanation for why he stopped his grandfather entering the flat after his father had allegedly killed his mother and fled. But this action might have been an attempt to stop him seeing someone else in the flat, Mr Raffell said. He also said that at the time Siu-tong said his father had throttled his mother, mobile phone records proved Mr Ling was out of the area. And forensic evidence showing Ho had died of strangulation by a thin ligature was at odds with Siu-tong's evidence that he had seen Mr Ling use his hands or arm. Mr Stuart-Moore agreed Siu-tong's behaviour was puzzling, but said it had to be seen in the light that he was the only other person present in the flat who could have killed his mother. He also said it was an 'oddity' the boy did not call police or an ambulance. He said that while Siu-tong's story continually evolved and was riddled with lies, Mr Ling's story remained consistent and was able to be checked.