Summary Criminal Litigation UNIT 19 - Opinion Evidence, Experts, and Privilege

19. Opinion Evidence, Experts, and Privilege

Includes:
- The General Rule of Opinion Evidence;
- Expert Opinion Evidence;
- Non-Expert Opinion Evidence;
- Ultimate Issues;
- What is Privilege?
- Privilege Against Self-Incrimination;
- Legal Advice Privilege;
- Waiver of Privilege.



The General Rule of Opinion Evidence

F11.1 The general rule of opinion evidence is that witnesses may only give
evidence of facts they personally believe and not evidence of their opinion.
- Such as inferences drawn from those facts (was driving 50mph in a 40 zone, as
opposed to driving too fast).
Inferences from the facts presented by a witness are to be drawn by the jury.

However, there are two exceptions to the general rule that exist in the cases of:
 Experts; and

 Non-experts.




Expert Opinion Evidence

, Use of Expert Opinion Evidence
Expert evidence may only be used for subjects which require for expertise, which a lay
person could not be expected to possess to a level that would enable them to understand the
evidence if unaided.
- If the tribunal of fact can form its own opinion without the assistance of an expert,
expert opinion evidence is inadmissible because it is unnecessary.
- A prime example is an expert’s opinion is not needed to aid a jury understand that memory
fades with the passage of time, but an expert opinion on childhood amnesia has been
admissible.

Expert opinion can also be used in where jurors can be expected to already have some
experience or knowledge of a particular area, in the narrow circumstance of the expert
having more knowledge, time, or better facilities to comprehend something. This can be
utilised to help a jury get up to speed.
- Such as with cell site data,

Expert evidence may be accompanied by animations to illustrate the opinion.

Who is an Expert?
F11.4 When instructing an expert, a party should be satisfied of their expertise in the
required area and that the expert is of a suitable calibre.
- Self-certification is not sufficient, specialised experience, knowledge, training, or
study is required.
- Police officers have been able to give evidence as to gang practices or how an
accident occurs if it is within their specialty.
- Doctors have been allowed to give evidence as to what may cause a cut (blunt or
sharp instrument) if it is within their specialty or even prove calculations on areas
not within their expertise, if they have refreshed their memory.
- The general point is that the knowledge ought to exceed anecdotes and would not
be naturally available to a jury (peritus by way of business).
The Crown must also take all necessary steps to ensure that the inappropriate expert
witnesses are not called.

In the majority of cases, the judge will be able to bake a decision on suitability from written
material although, in some cases, a vior dire hearing may be necessary to decide whether a
witness should be allowed to give expert evidence.
- If the judge decides that the expert does not defence their status, they can remove it and
limit their evidence to factual matters.

Duty of Experts
F11.37 An expert must help the court to achieve the overriding objective by giving their
unbiased opinion on matters within their areas of expertise and by actively assisting the court in
fulfilling its duty of case management.

This duty overrides the expert’s duty to whoever instructs or pays them and will require:
a) The expert to define their area of expertise in a report and when giving evidence;
b) Draw the courts attention to any question that would be outside of their own area
of expertise; and
c) To inform all parties and the court if their opinion changes at any time from that
contained in their report or statement.

Weight of Expert Evidence