Dlugosz, R. v

Expert evidence on a low-template mixed DNA profile may be admissible without a random-match probability or a verbal hierarchy of support. The judge must be satisfied that the opinion rests on a sufficiently reliable scientific basis. This requires detailed evidence of the expert’s relevant experience and features of the particular profile capable of supporting the opinion.

If admitted, the jury must be told that the opinion is experience-based, subjective and of limited assistance, rather than conventional statistical DNA evidence. Evidence that a defendant may be a contributor, or cannot be excluded, may itself be relevant and admissible.

Three conjoined appeals concerned the admissibility and use of mixed, low-template DNA evidence for which no conventional statistical evaluation could be given.

Dlugosz appealed convictions for burglary, robbery and manslaughter. DNA recovered from chisels was a complex mixture, and the Crown also relied on intercepted calls and bad-character evidence. Pickering appealed a conviction for sexual assault on a child. A mixed DNA profile and amylase were found on the complainant’s knickers. MDS appealed convictions for murder and related robbery offences. DNA evidence connected him as a possible contributor to material recovered from a doorbell, knife and cling film.

The common issue was whether, and on what basis, mixed-profile DNA evidence could be admitted where no random-match probability was available.

1. Disposition. The court dismissed Dlugosz’s appeal against conviction and Pickering’s appeal against conviction. It allowed MDS’s appeal for separate reasons, quashed his convictions and ordered a retrial. Pickering’s Sexual Offences Prevention Order was varied by agreement.
2. Admissibility of evaluative mixed-DNA evidence. A statistical random-match probability is not an indispensable condition of admissibility. Nor must an expert use a hierarchy or sliding scale of verbal support. The governing question is whether there is a sufficiently reliable scientific basis for the proposed opinion. An experience-based opinion may satisfy that requirement if the expert’s experience is fully set out and the particular mixed profile has features capable of supporting the evaluation.
3. Judicial and jury safeguards. Where admissibility is challenged, the judge must scrutinise both the expert’s experience and the profile’s features. If the evidence is admitted, the jury must receive a clear explanation that it has no statistical basis, differs from ordinary DNA evidence based on match probability, and is only a limited opinion based on experience. Those safeguards will generally prevent unfair or misleading weight being given to the evidence.
4. Application to Dlugosz and MDS. The experts’ opinions were admissible. In Dlugosz, all of the appellant’s alleles appeared in the mixture and several were prominent. In MDS, the expert had a sufficient experiential basis. The court reached the same general conclusion as R v Ashley Thomas [2011] EWCA Crim 1295.
5. Possible-contributor evidence. In Pickering, the evidence did not purport to evaluate the likelihood of contribution. It established only that he could not be excluded and that the findings were consistent with either account. That was relevant evidence, capable of being assessed with the evidence of amylase and the other evidence at trial.
6. Bad character. The admission of Dlugosz’s previous convictions under the Criminal Justice Act 2003 was within the trial judge’s discretion. They were not strict similar-fact evidence, but their similarities and relevance to propensity and other issues justified admission without unfairness.

• Court of Appeal (Criminal Division). Dlugosz’s conviction appeal was dismissed. Pickering’s conviction appeal was dismissed, but the Sexual Offences Prevention Order was varied. MDS’s appeal was allowed, his convictions were quashed and a retrial was ordered for reasons not published in the judgment.
• Central Criminal Court. Dlugosz was convicted before HHJ Gordon of burglary, robbery and manslaughter.
• Crown Court at Birmingham. Pickering was convicted before HHJ Chambers QC of sexual assault on a girl under 13.
• Central Criminal Court. MDS was convicted before HHJ Pontius of murder and other robbery-related offences.