Shirley v R

Where fresh DNA evidence undermines a central evidential basis for a conviction, the appellate court must assess whether any alternative explanation essential to the prosecution case is established to the criminal standard. A speculative possibility of an unknown prior sexual partner cannot sustain the conviction. The remaining circumstantial evidence must be sufficiently strong to displace the probability arising from the fresh scientific evidence. If it cannot do so, the conviction is unsafe and must be quashed.

The appellant was convicted of murder at Winchester Crown Court in 1988 and sentenced to life imprisonment. His earlier application for leave to appeal was refused in 1989.

Following a reference by the Criminal Cases Review Commission under section 9(1) of the Criminal Appeal Act 1995, he appealed on the basis of fresh DNA profiling of semen found in intimate swabs from the victim. The Crown accepted that the DNA showed a male contributor other than the appellant. To preserve the conviction, it contended that the appellant and an unidentified earlier sexual partner had both contributed DNA.

The central issue was whether the Crown's proposed second contributor was established to the criminal standard and, if not, whether the other circumstantial evidence could nevertheless make the conviction safe.

1. Appeal allowed; conviction quashed. The court held that the conviction was plainly unsafe in light of the fresh DNA evidence.

2. The Crown accepted that the DNA evidence disclosed a male contributor who was not the appellant. Its case could survive only if the court were sure that an unidentified man had had sexual intercourse with the victim before the killing, leaving DNA in the intimate swabs, while the appellant alone committed the rape and murder. This was not merely a possible explanation: it had to be proved to the criminal standard.

3. The scientific evidence, the absence of semen on the victim's knickers, and the evidence of her movements made it overwhelmingly probable that all the semen in the swabs had been deposited by one man on one occasion, namely her killer. The alleged prior intercourse and the identity and location of the supposed second contributor were wholly speculative. The late report concerning the persistence of sperm did not materially alter that assessment.

4. The remaining circumstantial evidence could not displace that probability. The evidence of injuries to the appellant was weakened by the condition of the victim's fingernails and the absence of evidence that the injuries were noticed after the killing. The shoe impression was not sufficiently distinctive. Fresh material also raised a substantial question mark over the prosecution timing case and the alleged missing half hour. The additional matters relied on by the Crown were insubstantial.

5. Since the court's conclusion that there was one male DNA contributor meant that the appellant could not have been that contributor, the conviction could not stand.

• Court of Appeal (Criminal Division): On a Criminal Cases Review Commission reference, the court allowed the appeal and quashed the conviction: [2003] EWCA Crim 1976.

• Full Court: The appellant's earlier application for leave to appeal against conviction was refused on 4 May 1989.

• Winchester Crown Court: In 1988, following a ten-day trial before Hutchison J, the appellant was convicted of murder and sentenced to life imprisonment.