Lord Ackner:

This is an appeal by special leave from a judgment of the Court of Appeal of Hong Kong (Yang CJ, Kempster JA and Macdougall J) given on 4 May 1988, dismissing the appellants'appeals against their convictions of murder on 13 November 1987, after a trial by jury presided over by Addison J. At the conclusion of the hearing on 2 November their Lordships agreed humbly to advise Her Majesty that the appeals ought to be allowed, the convictions quashed and that there be no order for retrial, for reasons to be given later. They now give their reasons.

The Facts

The facts out of which the prosecution arose can be shortly stated. At about 2.30 p.m. on 29 August 1989 a twelve year old boy called Kwan Ho-lun saw four men chasing the victim Peng Shao-chiang on the Yuen Chau Kok Temporary Housing Estate Shatin. At least three of the men had knives and were chopping at him as they ran. As a result he suffered severe injuries and later died on the same afternoon in hospital.

When the attack took place there were several police officers in the vicinity who gave chase. One of the men Leung Chi-fai, surrendered, but the others escaped. On 12 December 1986 Leung was indicted with murd