All relevant material must be disclosed, including facts detrimental to the opinion

The quashing of Sally Clark's conviction for the murder of her sons Christopher and Harry has inevitably been followed by questions about the role of the medical experts, in view of their failure to disclose key evidence and the role such evidence played in securing her conviction.1 The debate has been played out across the media, not least in the pages of the BMJ and on its website. 2 3

Medical experts are called on daily to deliver their opinions in both civil and criminal cases. Critics have focused their attention mostly on criminal trials. The initial involvement of an expert may be through professional duties, as in the case of the forensic pathologist who performs an autopsy and then finds that evidence from the autopsy report is being used by the prosecuting authorities in a criminal trial. Other experts may be called on by the police or by the Crown Prosecution Service.

In the adversarial systems of law in the United Kingdom the defence is also entitled to seek appropriate experts. Expert witnesses are in a very privileged …