Dlugosz v REGINA

Factual and Procedural Background

This opinion arises from appeals concerning the admissibility of Low Template DNA evidence derived from mixed samples involving at least two or three contributors. The central procedural context involves three separate appeals where the Crown sought to admit such DNA evidence against the appellant. The appellants challenged the admission of this evidence primarily on the basis that no random match probability statistics could be provided. The appeals involve trials of three appellants: the first convicted of burglary, robbery, and manslaughter; the second convicted of sexual assault; and the third convicted of murder and related offences. Each trial involved complex mixed DNA profiles, and the judges admitted the DNA evidence despite the absence of statistical match probabilities. The appeals examine the reliability, admissibility, and presentation of such DNA evidence, as well as the use of bad character evidence in one appeal. Procedurally, the court also considered the admissibility of expert evidence, the application of previous case law, and the appropriate directions to juries.

Legal Issues Presented

1. Whether Low Template DNA evidence derived from complex mixed profiles without available random match probability statistics is admissible as expert evidence.
2. Whether an expert must provide evaluative opinions using a statistical hierarchy or sliding scale to support the admission of DNA evidence.
3. What constitutes a sufficiently reliable scientific basis for admitting evaluative opinions in the absence of statistical calculations.
4. How to properly present such DNA evidence and its limitations to a jury to avoid misleading them.
5. Whether bad character evidence is admissible when the DNA evidence is contested and potentially weak.
6. The extent to which unpublished or un-peer-reviewed statistical methods can be admitted as expert evidence.

Arguments of the Parties

Appellants' Arguments

• The appellants contended that without statistical evidence of match probability, evaluative DNA evidence should not be admitted, as the jury requires a firm scientific basis to assess significance.
• They argued that expert opinions must be expressed using a hierarchy or sliding scale of support for admissibility.
• It was submitted that subjective opinions without statistical underpinning risk misleading juries and debasing the "gold standard" of DNA evidence.
• In one appeal, it was argued that bad character evidence should not be admitted to bolster weak DNA evidence.
• One appellant submitted that unpublished simulation experiments and statistical software lacked sufficient peer review and scientific reliability to be admitted.

Respondent's (Crown's) Arguments

• The Crown submitted that evaluative opinions based on expert experience, even without statistical match probabilities, can be admissible if there is a sufficiently reliable scientific basis.
• The Crown argued that experts need not use a sliding scale or hierarchy and may express opinions using other evaluative phrases, provided the jury is properly directed on their subjective nature.
• They contended that the jury can assess the weight of such evidence if limitations are clearly explained.
• The Crown relied on prior case law, including R v Ashley Thomas, to support the admission of expert opinions without statistical evaluation.
• Regarding bad character evidence, the Crown argued it was relevant and properly admitted as the DNA evidence was admissible and sufficiently probative.
• The Crown maintained that unpublished statistical methods were not yet admissible due to insufficient validation.

Table of Precedents Cited

Court's Reasoning and Analysis

The court undertook a detailed examination of the admissibility of Low Template DNA evidence derived from complex mixed profiles where statistical random match probabilities could not be calculated. It acknowledged the scientific difficulties inherent in such evidence, including the inability to attribute alleles to specific contributors and the impossibility of determining the timing or origin of DNA transfer.

The court rejected the appellants' argument that evaluative opinions must be supported by statistical evidence or expressed using a formal hierarchy or sliding scale. Instead, it emphasized that expert evaluative opinions based on sufficient experience and a sufficiently reliable scientific basis may be admitted, provided the limitations and subjective nature of such opinions are clearly explained to the jury.

The court reviewed the prior decision in R v Ashley Thomas, which held that expert opinions without statistical evaluation are admissible if given with appropriate caution and jury directions. It found no reason to depart from that approach and recognized that the absence of a statistical basis does not preclude the admission of expert opinion evidence.

The court considered the experts' experience in interpreting mixed DNA profiles and noted the need for commercial providers to make data available for independent scrutiny under the supervision of the Forensic Science Regulator to improve the scientific basis of such opinions. It stressed that judges must scrutinize the expert's experience and the specific features of the DNA profile when assessing admissibility.

Regarding jury directions, the court underscored the importance of informing juries that evaluative opinions without statistics are subjective and of limited assistance compared to conventional DNA evidence with statistical match probabilities. The court also encouraged the development of standardized written materials explaining DNA science for juries.

In the appeals concerning bad character evidence, the court applied the statutory framework and found the evidence admissible due to relevant similarities and propensity considerations, concluding that the overall fairness of the trial was preserved.

Finally, the court upheld the trial judges' decisions to admit the DNA evidence in all appeals, finding that the evidence was relevant and the jury was properly directed to assess its weight and limitations. In the third appeal, despite upholding the admissibility of the DNA evidence, the court allowed the appeal on other grounds and ordered a retrial.

Holding and Implications

The court held that Low Template DNA evidence derived from complex mixed profiles without available statistical random match probabilities is admissible as expert evaluative opinion evidence, provided there is a sufficiently reliable scientific basis grounded in the expert’s experience and the features of the DNA profile.

The court emphasized that such evidence must be presented to the jury with clear directions explaining its subjective nature, the absence of statistical underpinning, and its limited probative value compared to conventional DNA evidence. The court rejected the necessity of a formal sliding scale or hierarchy of expressions for admissibility.

Bad character evidence may be admitted if relevant and fair, even when DNA evidence is contested, provided the statutory criteria are met.

The decision reinforces the admissibility of expert opinions based on experience in forensic science where statistical data is unavailable, but underscores the need for transparency, rigorous scrutiny of expert credentials and experience, and careful jury directions to avoid prejudice or misunderstanding.

No new precedent was created beyond confirming and elaborating the principles established in R v Ashley Thomas and related authorities. The ruling calls for improved scientific validation and transparency in forensic DNA interpretation practices.