Puaca, R v

Where a conviction for murder depends substantially on disputed pathological evidence, fresh expert evidence which removes the main foundation for the prosecution theory may render the conviction unsafe.

An expert opinion must be objectively and scientifically reached. The expert must state its factual basis and address material matters that may undermine it. Evidence that is merely consistent with a conclusion has no probative value where it is equally consistent with a competing cause of death.

Where competing experts cannot be resolved by the jury without supporting evidence, a conviction cannot safely rest on one expert's opinion alone. Other evidence must make the jury sure of the alleged cause of death.

The appellant was convicted at Ipswich Crown Court of murdering Jacqueline Tindsley by smothering her in bed. The prosecution case depended principally on Dr Heath's pathological opinion that damage to both infraspinatus muscles showed that she had struggled while being restrained.

The defence relied on pathologists who considered that a mixed drug overdose, possibly accompanied by a fit, was the more likely cause of death. On appeal, further pathological evidence suggested that inflammation in the damaged muscles meant that the injury could have preceded death by hours.

The central issues were whether the fresh evidence was admissible and whether the pathological evidence, the summing-up, and the remaining non-expert evidence permitted the conviction safely to stand.

1. Appeal allowed and conviction quashed. The court was wholly satisfied that the murder conviction was unsafe.
2. The fresh pathological evidence satisfied Criminal Appeal Act 1968, section 23. It showed that the shoulder-muscle injury may have occurred hours before death. The injury could therefore not support an inference that the deceased had struggled while being smothered. That removed the principal, and perhaps only, basis for Dr Heath's conclusion.
3. Independently, Dr Heath's conclusion could not safely be relied on. His initial report did not address the toxicological findings or the absence of expected features supporting forced airway obstruction. A pathologist's opinion must be objectively reached, scientifically valid, and comply from the outset with the duties of an expert witness. The court endorsed the principle in National Justice Compania Naviera SA v Prudential Assurance Co Ltd (The “Ikarian Reefer”) [1993] 2 Lloyd's Rep. 68 that an expert must state the facts or assumptions relied on and must not omit material facts which may detract from the opinion.
4. Much of Dr Heath's evidence was expressed as findings consistent with asphyxia, without making clear whether that meant asphyxia generally or smothering by upper-airway obstruction. In re-examination he accepted that, apart from the muscle damage, those findings were also consistent with death by overdose. Such consistency evidence had no probative value on the disputed cause of death and risked misleading the jury. His reliance on matters later abandoned or treated as insignificant further undermined the safety of the verdict.
5. The prosecution properly conceded that, given the expert conflict, the jury could not convict on Dr Heath's evidence alone. The remaining evidence did not make the jury sure that death occurred by smothering or while the appellant was awake. The summing-up did not clearly direct the jury that acquittal was required in those circumstances.

• Court of Appeal (Criminal Division): By [2005] EWCA Crim 3001, allowed the appeal and quashed the conviction as unsafe.
• Crown Court at Ipswich: On 22 November 2002, following trial before His Honour Judge Mellor, convicted the appellant of murder.