15. Opinion Evidence - Expert Evidence Flashcards
Meaning of opinion evidence
Any inference from observed or assumed facts
As a general rule, witnesses should only speak to that which was directly observed by them
Categories of permissible opinion evidence
Expert Opinion
Opinions where facts and inferences are impossible to separate
Non-opinion expert evidence
Non-expert opinion evidence
Permissible opinion evidence
[Opinions where facts and inferences are impossible to separate]
Where inferences drawn by witnesses arising from their perception, classification, recollection.
Examples: statements concerning speed, temperature, identity of person, things, and handwriting, sobriety, emotional state
Where they consist of both fact and inference
Permissible for a maid to “record the immediate impression formed on her mind on entering a room occupied by her mistress and a man, as to whether intercourse had taken place between them”.
Permissible opinion evidence
[Non-opinion expert evidence]
Use of expertise to identify facts which may be obscure or invisible to a lay witness. For example:
- Chemist explaining how a drug operates in the body
- How to interpret a reading from an instrument
- Meaning of a foreign word
- Medical diagnosis based on an x-ray
Permissible opinion evidence
[Non-expert opinion evidence]
Cases where experience is derived from past general experiences, (sometimes called pseudo-expert evidence) such as:
How a machine they are familiar with performs under certain conditions
How a vehicle they drove frequently behaves
Permissible opinion evidence
EXPERT OPINION EVIDENCE
Criteria for reception of expert evidence
Makita (Australia) Pty Ltd v Sprowles - Heydon JA’s 7 step test for admission for expert opinion evidence
- Must be demonstrated that there is a FIELD OF SPECIALISED KNOWLEDGE required for trier of fact to understand a particular subject of investigation;
- There must be an IDENTIFIED ASPECT OF THAT FIELD in which the witness demonstrates that by reason of specified training, study or experience, the witness has BECOME AN EXPERT;
- The opinion proffered must be WHOLLY OR SUBSTANTIALLY based on the witness’s expert knowledge;
- The expert must identify the assumptions of primary fact on which the opinion is offered (the assumption identification rule);
- Basis rule: opinion may only be given by expert witness where there is or will be proof, by other admissible evidence, of the facts and assumptions upon which the opinion is based
The opinion is not admissible unless evidence has been, or will be, admitted (whether from expert or some other source) which is capable of supporting findings of primary fact “sufficient like” those factual assumptions to render the expert opinion of value [the basis rule] (ie, requirement that there be evidence capable of sustaining findings of fact having some correspondence with the expert’s factual assumptions)’
- Must be a demonstration that the facts on which the opinion is based form a PROPER FOUNDATION for it;
- The opinion requires DEMONSTRATION OR EXAMINATION OF THE SCIENTIFIC or other intellectual basis OF THE CONCLUSION REACHED
Admission of expert opinion evidence
Requirement there be a field of specialised knowledge
Criterion requires proof of a field of specialised knowledge
Does NOT require evidence that there be a “general acceptance in the particular field to which it belongs”
Rather: provided the judge is satisfied that there is a field of expert knowledge to which recourse may be had, an expert’s view within that field may be admissible even if those views are not shared by other experts in the field.
NOTE: expertise can be derived from multiple areas including “through formal training, scholastic studies, or practical experience”
Example: aboriginal tracker who trained from age 7
Heroin addict identifying substance as heroin
Police officer giving opinion on whether drugs were for personal use or supply
Admission of expert opinion evidence
Identification and proof of assumed facts (assumptions identified by the expert)
Evidence from the witness giving expert opinion must identify the facts to which the expert applies specialised knowledge in order to arrive at the expert opinion in question.
Some facts may be provable, other may be assumed. The expert must “provide identification of the facts they are assuming to be true, so they can be measured against the evidence”.
Note: failure to prove the assumed factual basis of an expert opinion goes to inadmissibility (relevance), not merely weight
Admission of expert opinion evidence
Basis rule
Basis rule: expert opinion is not admissible unless evidence has been, or will be, admitted from the expert or from some other source, which is capable of supporting findings of primary fact which are sufficiently like the factual assumptions on which the opinion is based to render the opinion of value.
Examples:
(a) Expert evidence that a pole was in a dangerous corroded condition was held incapable of amounting to corroboration where the expert had not seen the pole, but instead relied on another expert’s description
(b) Expert opinion on the faults in an electrical heater held inadmissible where witness had not examined the heater but another one of a similar make
(c) Expert opinion evidence which relied on inadmissible evidence is itself inadmissible
Admission of expert opinion evidence
Intellectual basis of opinion
Expert witness must:
- demonstrate that the opinion is wholly or substantially based on the witness’s expert knowledge;
- demonstrate that the facts on which it is based form a proper foundation or it;
- demonstrate the scientific/intellectual basis for the conclusions reached.
Duty of an expert witness
r 429F UCPR
To assist the court, but not to be an advocate for a party.
Argumentative or adversarial evidence may be rejected in a report and will impact weight to be given to report.
Ultimate Issue rule for experts
An expert witness may not be asked the question which the court itself has to decide [ultimate issue rule].
Can be a fine line. For example:
(a) Not permissible for an expert to say a solicitor was negligent in doing or not doing something
(b) Would be permissible for an expert to say: what the ordinary industry wide practice is, admit evidence as to common practice for solicitors, evidence of how long it would typically take a solicitor to do something, etc
Opinion evidence in the EAC - key sections
Section 76 - Opinion evidence is inadmissible
Section 77 - Exception: non-opinion purpose [where evidence of opinion is admitted for a purpose other than proof of the existence of a fact]
Section 78 - Lay opinions (opinions which were seen, heard, perceived) where necessary to obtain understanding of event/matter.
Section 79 - Opinion based on specialised knowledge where opinion is “wholly or substantially based on that knowledge” [broader test than common law equivalent].
Section 80 - Evidence of an opinion is NOT inadmissible only because it is about the ultimate issue, or a matter of common knowledge
