Opinion Evidence Notes

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...

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