Expert Evidence in Criminal Proceedings

Current project status

  • Initiation: Could include discussing scope and terms of reference with lead Government Department
  • Pre-consultation: Could include approaching interest groups and specialists, producing scoping and issues papers, finalising terms of project
  • Consultation: Likely to include consultation events and paper, making provisional proposals for comment
  • Policy development: Will include analysis of consultation responses. Could include further issues papers and consultation on draft Bill
  • Reported: Usually recommendations for law reform but can be advice to government, scoping report or other recommendations

Addressing the admissibility of expert evidence in criminal proceeding.

Download the report

Download the consultation

The problem

In a criminal trial, a jury or magistrates’ court is required to determine disputed factual issues.

Experts in a relevant field are often called as witnesses to help the fact-finding body understand and interpret evidence with which that body is unfamiliar.

The current judicial approach to the admissibility of expert evidence in England and Wales is one of laissez-faire.

Too much expert opinion evidence is admitted without adequate scrutiny because no clear test is being applied to determine whether the evidence is sufficiently reliable to be admitted.

This problem is exacerbated in two ways:

First, because expert evidence (particularly scientific evidence) will often be technical and complex, jurors will understandably lack the experience to be able to assess the reliability of such evidence.

There is a danger that they may simply defer to the opinion of the specialist who has been called to provide expert evidence.

Secondly, in the absence of a clear legal test to ensure the reliability of expert evidence, advocates do not always cross-examine experts effectively to reveal potential flaws in the experts’ methodology, data and reasoning.

Juries may therefore be reaching conclusions on the basis of unreliable evidence. This conclusion is confirmed by a number of miscarriages of justice in recent years.

The project

We published a consultation paper on 7 April 2009, in which we made a number of provisional proposals which would reform the law governing the admissibility of expert evidence in criminal proceedings in England and Wales.

The consultation period closed in July 2009.

In our 2009 consultation paper we agreed with the view of the House of Commons’ Science and Technology Committee that a reliability test for expert evidence should be formulated in partnership with judges, scientists and other key players in the criminal justice system.

Our provisional view that there should be a new reliability-based admissibility test was broadly (but not universally) supported by our many consultees, including judges, scientists and other key players in the criminal justice system.

A summary of the responses we received is available.

Following consultation, we formulated our final recommendations, produced draft legislation and again consulted with judges, lawyers and experts.

Our recommendations

Our final recommendations and our draft Criminal Evidence (Experts) Bill are set out in the report we published on 22 March 2011, Expert Evidence in Criminal Proceedings in England and Wales.

In the report we recommend:

  • a new admissibility test for expert evidence
  • that expert opinion evidence would not be admitted unless it was adjudged to be sufficiently reliable
  • new guidance for judges for applying the test, setting out the key reasons why an expert’s opinion might be unreliable
  • a proper framework in criminal proceedings for screening expert evidence at the admissibility stage
  • codifying the uncontroversial aspects of the present law, so that all the admissibility requirements for expert evidence would be set out in a single Act of Parliament
  • giving the Criminal Procedure Rules Committee the power to create further procedural rules

The draft Criminal Evidence (Experts) Bill published with the report (as Appendix A) sets out the admissibility test that judges would apply to exclude unreliable expert evidence.


The Ministry of Justice responded on 21 November 2013, indicating that it did not intend to act on the majority of our recommendations at this time.

We have, however, achieved a great deal by other means:

  • The Criminal Procedure Rules Committee has adopted as many of the recommendations as it could through the Criminal Procedure Rules and accompanying Criminal Practice Directions. As a result, while the common law remains the source of the criteria by reference to which the court must assess admissibility, the Rules list those matters which must be covered in the experts’ report so that the court can conduct such an assessment and the Practice Directions list the factors the court may take into account in determining the reliability of expert opinion.
  • Meanwhile, in a parallel development, a series of cases concerned mainly with the use of Low Template DNA has established a requirement that the court can only admit expert evidence if it is reliable.
  • In a development at least as significant as the other two, the Advocacy Training Council has adopted our recommendations in this report as the basis for its training. In this way, we are confident that the entire approach of the profession to expert evidence in both criminal and civil proceedings can be fundamentally reformed and the risk of miscarriages of justice greatly reduced.


Documents and downloads

Project details

Area of law

Criminal law


Professor David Ormerod QC