Commentary on Sections Part 11 - Evidence Chapter 2: Hearsay evidence Section 127: Expert evidence: preparatory work
425.This section seeks to address the problem which arises where information relied upon by an expert witness is outside the personal experience of the expert (for example work undertaken by an assistant) and cannot be proved by other admissible evidence. The intention is that the rules about advance notice of expert evidence will be amended so as to require advance notice of the name of any person who has prepared information on which the expert has relied. It is envisaged that any other party to the proceedings will be able to apply for a direction that any such person must give evidence in person but a direction will only be given if the court is satisfied that it is in the interests of justice.
426.In cases where no such application is made in respect of any assistant listed, or an application is made but refused, section 127 will enable the expert witness to base his evidence on any information supplied by that assistant on matters of which that assistant had personal knowledge. Section 127 applies if:
	The statement was prepared for the purpose of criminal proceedings;
	The expert’s assistant had or might reasonably be supposed to have had personal knowledge of the matters stated; and
	A notice has been given under the advance notice rules of the name of a person who has prepared a statement on which it is proposed that the expert witness should base any opinion or inference, and the nature of the matters stated.
427.Where section 127(1) applies, the expert may base an opinion or inference on the statement and any information so relied upon will be admissible as evidence of its truth.
428.Subsections (4) and (5) permit a party to the proceedings to apply for an order that the exception should not apply in the interests of justice. In deciding whether to make such an order, the court may take into account any of the matters mentioned in subsection (5).