Criminal and civil cases

• The general rule is that courts can hear evidence of fact not opinion but there are a number of exceptions.

• Under the common law expert opinion is admissible where the matter is outside the experience of judge or jury.

• The judge decides on admissibility both if court should be assisted and if expert has the required expertise.

• Expertise is decided on a case-by-case basis.

• The expert gives opinion on basis of facts which must be proved by admissible evidence.

Criminal cases only

• The common law principle is that an expert cannot give an opinion on the very fact the tribunal has to decide (the ultimate issue rule) but in practice this is often ignored.

• The Criminal Procedure Rules 2015 applies where a party wants to introduce expert opinion evidence.

Civil cases only

• The Civil Procedure Rules (CPR) set out details of how expert evidence is to be presented including the use of court appointed experts.

• The ultimate issue rule has been abolished by s33(1) Civil Evidence Act 1972.