Weller, R. v

In DNA cases, strict compliance with Part 33 of the Criminal Procedure Rules assists a fair trial by identifying agreed evidence and refining the true expert issues for the jury.

An expert may evaluate competing mechanisms of DNA transfer where there is a sufficiently reliable scientific basis. That basis may include published research, unpublished work and practical professional experience. Publication is not a prerequisite to reliability. The factual basis and material relied upon must be capable of being tested, including by cross-examination.

A post-trial expert report is not fresh evidence where it establishes no reliable challenge to the trial experts’ evaluative evidence and leaves the conviction safe.

Peter Weller was convicted at Kingston Crown Court of sexual assault by penetration and was sentenced to three years’ imprisonment. He obtained leave to appeal out of time on the basis of an asserted fresh expert report concerning DNA recovered from his left-hand fingernails.

It was common ground that the minor DNA profile was that of the complainant and that there were five possible transfer mechanisms. The trial experts agreed that vaginal contact was the most likely explanation, but differed over the strength of that conclusion.

The appeal raised whether the state of scientific knowledge permitted an expert evaluation of the relative transfer possibilities, and whether the new expert material amounted to fresh evidence making the conviction unsafe.

1. Appeal dismissed. The proposed fresh evidence did not show that the DNA evaluation admitted at trial lacked a sufficiently reliable scientific basis. The conviction was safe.
2. The court stressed that, in future DNA cases, Part 33 of the Criminal Procedure Rules should be followed strictly. Uncontroversial matters should be agreed and put before the jury in an agreed expert statement. The real issue between the experts should then be identified and refined.
3. On the facts, the scientific evidence justified an evaluation of the possible transfer mechanisms. Transfer from vomit or hair was difficult. The vagina was a DNA-rich source, and digital penetration was likely to transfer DNA. The unpublished study relied on by the appellant’s expert showed persistence of DNA after vaginal contact; it did not undermine the trial experts’ conclusion.
4. A court may consider an expert’s practical field experience and unpublished work when deciding whether expert evidence has a sufficiently reliable foundation. Such material is not excluded merely because it is unpublished. Applying R v Abadom 76 Cr.App.R 48, the court held that an expert may draw on others’ work once the primary facts are proved, provided the material is identified so that the opinion’s cogency can be tested.
5. The appellant’s new expert was a scholar without comparable practical DNA experience and did not identify a reliable scientific objection to the trial evaluation. There was therefore no fresh evidence. The medical evidence strongly supported the complainant, and the DNA evidence confirmed that the jury’s verdict was right.

• Court of Appeal (Criminal Division): Leave to appeal out of time was granted after preliminary hearings. The appeal, based on asserted fresh DNA expert evidence, was dismissed.
• Kingston Crown Court: The appellant was convicted on 30 November 2006 of sexual assault by penetration and was subsequently sentenced to three years’ imprisonment.