#10387 - Opinion Evidence - BPC Criminal Litigation (formerly BPTC) 2024/2025

OPINION EVIDENCE

General rule: Ws can only give evidence of facts they personally perceived, NOT evidence of their opinion (inferences drawn from those facts)

Court then forms its own opinion on the facts perceived by W.

Exceptions where opinion evidence allowed:

• Non-experts: statement of opinion on any matter not calling for expertise

• Experts: statement of opinion on any relevant matter calling for expertise may be made by a W qualified to give that opinion.

Non-Expert Opinion Evidence

When a W of fact states their opinion and the “opinion” is actually a statement of several facts – admissible as long as there is a proper appraisal of the facts.

• “Defendant was drunk”

• "I estimate that he was driving at over 100mph"

Facts which Witness saw/heard/smelled which led to this opinion.

Expert Opinion Evidence

Where issue Court is required to determine is far removed from the court's expertise – needs opinion of expert to help determine.

Expert opinion is admissible, but non-expert opinion should not be admitted.

Party calling expert should ensure his evidence is limited to matters within his expertise on relevant and admissible issues.

“Expert”

Where a case requires expert opinion - only a suitably-qualified expert can give it.

“Expert” - not necessarily require formal qualifications – requires specialised knowledge, information and study.

Is Expert Opinion Required?

Difficulty distinguishing when the Jury should determine the issue and when an expert opinion is required (Jury likely to accept)

Rule: Generally expert not required where offers opinion on normal human behaviour

“normal human behaviour” - expert may be called when Defendant suffering from recognised medical condition or personality disorder.

Bias

Party who wishes to call an expert should disclose to the court and other parties any interest the expert has or may seem to have.

Expert must disclose any potential conflict of interest – attach CV to Report.

Interest will not automatically disqualify – Consider nature and extent of connection/interest.

Expert must be aware of the overriding duty as an expert to the court, and willing and able to fulfil it

Apparent bias is not enough to disqualify BUT desirable expert should have no actual/apparent interest – if testifies may affect weight attached to opinion.

Status of Expert Evidence

Should be treated like the evidence of any other Witness

Misdirection:

• to tell Jury they must accept it, or

• to tell Jury can disregard it.

Risk: Experts can base evidence on sound foundation, but still end up unsure/contradictory.

Basis of Expert Opinion

Based on facts of case (primary facts), knowledge and resources (secondary facts).

Primary Facts

“Primary facts” - must be proved by admissible evidence

• e.g. valuation of vase –

  • primary facts: condition, design, colour, material

  • secondary facts: prices on markets, auction prices

If Expert performs a test on evidence to come to a conclusion – test is a primary fact and must be proved

• maximum use of written statements and formal admissions – to show test was properly carried out

Secondary Facts

Do not have to be proved - Information referred to is not hearsay but part of basis of opinion.

Can only be introduced by experts

• non-expert Witness cannot refer to a secondary fact (eg. a book) to support his opinion.

Notice of Expert Evidence

Prosecution obliged to disclose its expert evidence to Defence – Defence also obliged to disclose.

Crown Court:

• Must give other party written report of expert's findings/opinion.

• On request in writing – must provide a copy of/opportunity to examine the record of any observation, test or calculation opinion based on.

Need NOT disclose if party calling expert has reasonable grounds to believe that compliance might lead to:

• Intimidation or attempted intimidation of expert, or

• interference with the course of justice

Party must give notice of grounds for non-compliance to the other parties.

Failure to comply with rules – expert evidence can only be adduced with court's permission.

Expert Opinion & Hearsay

“Expert report” means a written report by a person dealing wholly/mainly with matters on which he is qualified to give expert evidence

If expert attends, report admissible without leave.

If expert does NOT attend, report admissible BUT leave required.

Applies to statements of fact and opinion in the Report – both are admissible.

Guidance for Experts

Crim PR, Part 33

r33.2 – Duty to court overrides duty to party calling him

Giving Evidence

Evidence given – should be and be seen to be the independent product of the expert uninfluenced as to form or content.

Expert should offer independent assistance to the court by stating objective unbiased opinion on matters within his expertise

Should never become, in effect, an advocate for the party

Expert should make it clear if a particular question/issue falls outside his expertise

Facts or assumptions upon which the opinion is based must be stated

Material facts that detract from the opinion should be stated.

If expert feels that he has been supplied with...