§ Mrs. Browning
To ask the Secretary of State for the Home Department what criteria are set for doctors and psychiatrists who offer themselves as expert witnesses on autistic spectrum disorders. 
§ Paul Goggins
[holding answer 15 June 2004]: In criminal law, where matters fall outside the ordinary knowledge of the court, the court may allow the opinions of an expert witness to be admitted as evidence. If either the prosecution or the defence wishes to adduce the evidence of an expert witness. they are obliged to disclose the expert's statement to the other side in advance of the trial. The other side may then request further details from the expert. This obligation also allows the other side sufficient time to prepare their arguments if they wish to challenge, the expert witness.
The decision whether or not to allow the evidence of an expert witness to be admitted rests with the court, which must be satisfied that the material comes within a recognized field of expertise and that the witness is indeed an expert in that field. It is for the jury to decide what weight ought to be placed on any expert evidence that has been admitted.
One exception to these general rules is that, under the Criminal Procedure (Insanity and Unfitness to Plead) Act 1991, a defendant shall not be acquitted on the grounds of insanity, or found unfit to plead, except on the evidence of two or more registered medical practitioners, at least one of whom is approved by the Secretary of State as having special experience in the diagnosis or treatment of mental disorder.1158W