A HIGH Court judge yesterday ruled that a businessman accused of taking part in the $167 million Kai Tak airport robbery should be acquitted. Mr Justice Duffy said the armed raid, the world's biggest cash robbery, must have been an inside job. Security guards had lied in court and the quality of evidence relating to the identification of the defendant was the worst he had ever seen, he said. 'The evidence, in my view, is of such a low quality I cannot allow it to go to the jury for their deliberation,' said the judge. 'I must direct the jury in this case to acquit the defendant.' The judge made his comments after hearing submissions from prosecution and defence barristers halfway through the trial. The jury was sent away while legal arguments were heard. The judge said he would direct the jury to return a not guilty verdict on their return to court this morning. The cash was stolen from a Guardforce van when it stopped outside the airport on July 12, 1992. The court heard Mr Justice Duffy had compiled a list of 15 weaknesses in the identification evidence which he would have had to bring to the jury's attention when summing up. Guardforce witnesses had been prepared to tell lies 'at the drop of a hat', said the judge. He added: 'It may well be this is because they are covering something up. As we all must acknowledge, as a matter of common sense, someone in Guardforce must have assisted in the commission of this robbery. 'It could not have been carried out without the co-operation of one of those vans.' Speaking of the identification evidence, Mr Justice Duffy said: 'I have come to the conclusion that it is inherently bad. 'It is so inherently weak, so improbable in many of its aspects that it would be a travesty for me to allow that evidence to be determined by a jury. 'It is the worst piece of identification evidence I have ever heard in all the years of experience I have had in the criminal courts.' The guilt or innocence of the defendant was not the question but the quality of the evidence put forward by the prosecution to establish his guilt, the judge said. Prosecution witnesses had lied, the court heard. Mr Justice Duffy said: 'One gets used to that in Hong Kong but one eventually becomes a bit fed up with it.' Witnesses expected jurors to put their blinkers on and convict defendants based on what they said. Cheung Tze-keung, 38, was alleged to have been one of three gunmen who stormed the security van, hijacked it, tied up the guards, and escaped with the cash. Van commander Yiu Chung-keung, 31, did not pick out Cheung in an ID parade. He later told police he recognised Cheung but had been too afraid to say so. The court heard the van carrying the cash should have been escorted by a second security vehicle. But this did not happen on the day of the robbery. The van containing the money was robbed when it stopped outside the airport vaults for formalities to be completed. Again, this was against regulations. This is the second time Cheung has been put on trial for alleged involvement in the robbery. In December 1992 he was found guilty by a jury majority of five to two and jailed for 18 years. But on September 7 last year, the Court of Appeal ordered a retrial after raising questions about the way in which that jury had been directed. Cheung was released from custody the following day. He was also sentenced to three years in jail for offering a bribe to a police officer investigating the robbery. The appeal against this conviction was dismissed. Having spent 1,000 days in custody, he has now served that sentence.