Opinion Evidence

Question 1

General rule on opinion evidence

Answer 1

• General rule is that witnesses may only give evidence of facts they personally perceived and not evidence of their opinion

Question 2

Exceptions to general rule on opinion evidence

Answer 2

• Two exceptions to the general rule:
• Non experts - a statement of opinion on any matter not calling for expertise, if made by a witness as a way of conveying relevant facts personally perceived by him or her, is admissible as evidence of what the witness perceived
• Experts - subject to compliance with Crim PR part 19, a statement of opinion on any relevant matter calling for expertise may be made by a witness qualified to give such an expert opinion

Question 3

Non expert opinion evidence

Answer 3

• A statement of opinion may be given by a witness, on a matter not calling for expertise, as a compendious means of conveying facts perceived by the witness.
• Examples:
• Handwriting which they are familiar with
• Voice which they recognise
• Evidence of person’s age
• General appearance of a person’s state of health, mind or emotion
• The value of a plate glass window
• However, not the value of less common objects such as antique art (which would require an expert)
• On a charge of driving when unfit through drink, a non-expert may give evidence of their impression whether the accused had taken drink, provided the facts are described

Question 4

Expert opinion evidence - competence of expert witness

Answer 4

• Occasionally statute prescribes required qualifications.
• Example: Jury cannot acquit on insanity without evidence from two registered medical practitioners.
• A person is not an expert merely by employment but may be competent if their organisation uses only qualified experts.
• Rarely a voir dire may be held to decide competence; usually a judge decides via written material.
• A judge may later limit a witness to factual matters only if expert status is withdrawn

Question 5

Matters calling for expertise

Answer 5

• Expert opinion is only admissible on subjects beyond the expected knowledge of lay persons (jurors/magistrates).
• Examples:
• • Childhood amnesia affecting memory
• • Mobile phone location via cell site data
• If a matter can be understood without expert input, then expert opinion is unnecessary and inadmissible

Question 6

Opinion on ultimate issues

Answer 6

• Old rule barring opinion on ultimate issues is largely obsolete.
• Experts must not usurp the role of the fact-finder.
• E.g., A psychologist can say a confession might be unreliable but cannot say it was

Question 7

Police officers opinion on identification

Answer 7

• Police officers may offer opinion on identification if they have reviewed footage extensively and their task cannot be replicated by the jury.
• They are not traditional ‘experts’ but may give opinion based on their unique viewing experience

Question 8

Certified experts

Answer 8

• An expert can become certified via the Expert Witness Institute.
• Certified experts:
• • Commit to ongoing development
• • Are reassessed every five years

Question 9

Duty of experts

Answer 9

• Duty is to the court and overrides obligations to instructing parties.
• Includes:
• (a) Declaring areas of expertise
• (b) Alerting court to questions beyond their expertise
• (c) Informing court and parties of any changes in opinion
• Involvement in investigation does not automatically disqualify the expert

Question 10

Functions and weight of expert evidence

Answer 10

• Experts give judges/juries tools to evaluate evidence.
• Jury must be told:
• • They are not bound by expert opinion
• • The final decision is theirs
• But, if the only qualified evidence supports one view, it cannot be ignored without justification

Question 11

Expert evidence in the case of diminished responsibility

Answer 11

• Where no other evidence contradicts expert medical opinion, the jury should accept it.
• If other relevant circumstances exist, medical evidence should be weighed in context