The opinion rule Flashcards
The general exclusionary rule
23 Opinion rule
A statement of an opinion is not admissible in a proceeding, except as provided by
section 24 or 25.
Section 23 states that opinions are not admissible to prove the truth of what is
believed or inferred. A witness is called to give evidence of what he or she
has experienced, and the testimony must comprise direct evidence of his or
her own perceptions of the facts. The premise of the general exclusionary rule
is that a witness’s opinions, beliefs or inferences are not their perceptions, but
are conclusions drawn from those perceptions.
The Act defines “opinion” as “a statement of opinion that tends to prove or
disprove a fact” (s4). The distinction between what is fact and what is opinion
is sometimes unclear.
The rationale of the exclusionary rule is essentially to prevent the admission
of unreliable, superfluous or misleading evidence. To admit such evidence
would result in the admission of evidence of doubtful relevance and be a
waste of court time. The justifications for the rule include that:
- where a witness offers a bare opinion it holds little probative weight
- there is a danger that a witness offering opinion evidence will “usurp” the
function of the tribunal of fact, which is to draw the necessary inferences
from the facts presented in evidence. The opinion evidence could confuse
the tribunal of fact and prolong proceedings. - a witness’s evidence of opinion may be based on other evidence which, if
stated expressly, would be inadmissible (for example, where an opinion is
based largely on propensity evidence).
Sections 24 and 25 are exceptions to the general exclusionary rule set out in
s23. It can be assumed that the intention is that a statement of opinion that is
admissible under ss 24 or 25 should also satisfy any other rules that apply
under the Act (for example, the propensity rules).
Non-expert opinion evidence
24 General admissibility of opinions
A witness may state an opinion in evidence in a proceeding if that opinion is necessary
to enable the witness to communicate, or the fact-finder to understand, what the
witness saw, heard, or otherwise perceived.
Opinion evidence from a witness may include topics such as identity, speed,
emotional state, weather, age and so on, but the list of areas in which nonexpert opinion is admissible is not limited.
In order to be admissible under s24, the statement of opinion must fulfil two
basic criteria:
* opinion must be the only way in which to effectively communicate the
information to the finder of fact,
* the witness must be stating an opinion (be it conclusion, inference etc)
from something personally perceived.
In general, non-expert opinion evidence will be accepted where the
perceptions and statements of fact of the witness are conclusions in
themselves, or where there is a mixture of inference and fact that cannot be
separated.
For example, where a witness offers evidence that she identified the offender
in an identification parade, she is giving evidence of the fact that she chose
the person from a parade of other people, but the belief that the person and
the offender are one and the same is a mixture of fact and inference. The two
are almost impossible to separate.
Similarly, where a witness gives evidence about a car accident, he or she may
be asked whether the car was speeding. The witness may use the sound of the
car or other perceptions to give an opinion on whether the car was travelling
at a fast speed: the perception and the opinion are closely bound together.
Admissibility of expert opinion evidence
Where a matter calls for special skill or expertise, only a witness who is an
expert in the matter can give evidence, and the range of opinion evidence is
limited to matters where the opinion is needed in order to illuminate the facts
in the case. This means that if facts can be stated without reference to an
opinion, the expert is not allowed to express an opinion on the matter.
Section 25 governs the admissibility of expert opinion evidence:
25 Admissibility of expert opinion evidence
(1) An opinion by an expert that is part of expert evidence offered in a proceeding is
admissible if the fact-finder is likely to obtain substantial help from the opinion in
understanding other evidence in the proceeding or in ascertaining any fact that is of
consequence to the determination of the proceeding.
(2) An opinion by an expert is not inadmissible simply because it is about—
(a) an ultimate issue to be determined in a proceeding; or
(b) a matter of common knowledge.
(3) If an opinion by an expert is based on a fact that is outside the general body of
knowledge that makes up the expertise of the expert, the opinion may be relied on by
the fact-finder only if that fact is or will be proved or judicially noticed in the
proceeding.
(4) If expert evidence about the sanity of a person is based in whole or in part on a
statement that the person made to the expert about the person’s state of mind, then—
(a) the statement of the person is admissible to establish the facts on which the
expert’s opinion is based; and
(b) neither the hearsay rule nor the previous consistent statements rule applies to
evidence of the statement made by the person.
(5) Subsection (3) is subject to subsection (4).
Section 25 is concerned only with the admissibility of expert opinion
evidence. Expert evidence may consist of fact, opinion, or a mixture of the
two (s4). Factual evidence from an expert will be governed only by the
general rules in ss7 and ss8, and any other admissibility rules applicable in
the individual case.
If the evidence is opinion evidence, then in order to comply with s25, the
opinion must
* be that of an “expert”
* comprise “expert evidence”, and
* offer substantial help to the fact-finder in understanding other evidence or
ascertaining any fact in the proceeding.
Qualification as an expert
Section 4 of the Act defines an “expert” as “a person who has specialised
knowledge or skill based on training, study or experience”. The judge must
determine whether the expert witness is properly qualified to testify: opinions
given by non-experts on matters calling for expertise are inadmissible.
The expert is required to demonstrate to the court that he or she has the
requisite qualification to be deemed “expert” in the field in question; the
expert may be qualified through formal study and training, from experience,
or both. Evidence offered by an expert should be within his or her area of
expertise.
“Likely to obtain substantial help”
Section 25(1) provides that expert opinion evidence will be admissible if the
fact-finder is likely to obtain substantial help from the opinion in:
* understanding other evidence, or
* in ascertaining any fact that is of consequence in the determination of the
proceeding.
“Substantial help” replaces the two defining common law rules that related to
expert opinion evidence and are abolished in s25(2): the common knowledge
and ultimate issue rules. The common knowledge rule stated that an expert
could not give an opinion on matters that were within the common knowledge
of the jury. The ultimate issue rule provided that an expert could not give an
opinion on the ultimate issue in the case.
The requirement of substantial helpfulness seeks to offer a “more rational test
that assesses the reliability and value of the expert opinion on its merits”. The
Court in B v R25 held that it “necessitates consideration of an amalgam of
relevance, reliability and probative value”.
Evidence based on proven facts
Opinion based on facts outside the general body of information will need to
be proved or judicially noticed. In R v Turner26 the Court said that:
“Before a court can assess the value of an opinion it must know the facts upon
which it is based. If the expert has been misinformed about the facts or has
taken irrelevant ones into consideration or has omitted to consider relevant
ones, the opinion is likely to be valueless. In our judgment, counsel calling an
expert should in examination in chief ask his witness to state the facts upon
which his opinion is based. It is wrong to leave the other side to elicit the
facts by cross-examination.”
The factual basis of an expert opinion needs to be proved as, without it, the
opinion can be given little weight. Indeed, where there is no proven factual
basis, the evidence may carry so little weight that it will not be relevant.
Where current knowledge does not allow an opinion based on proven facts,
then the expert should indicate that he or she cannot express a view.
- Where material, such as books and journal articles, contribute to the
general body of information on any given topic, an expert witness is
allowed to base his or her opinion partly on this information: to do
otherwise would involve a costly and time-consuming parade of experts in
court. (For example, research on memory processes has been conducted
by a large number of scientists, the results of which make up a body of
knowledge, but no one scientist has personally conducted a sufficient
number of experiments to be able to give a full breadth of comment on the
basis of personal experience alone.) - An expert opinion may also be based on facts that are supplied by others,
such as analyses of body tissues carried out by colleagues, or the research
findings of other scientists. In this way, the facts on which an expert
witness bases his or her opinion may be assumed facts, or facts of which
they have no first-hand knowledge (for example, where there are marks
on a body, a surgeon who has not seen the body may be asked whether,
given the nature of the wounds, they could be self-inflicted). The expert
should state the assumed facts on which the opinion is based, and the
admissible evidence offered is the assumed facts themselves. If research
findings were relayed directly to the court, rather than being used to
support and explain the conclusions reached by the expert witness, they
would be hearsay evidence and may be excluded under s18.
Section 129 can act to allow published documents to be admitted as evidence
where the Judge decides that they are reliable sources, without having to have
recourse to the rules relating to opinion evidence. Where an expert has his or
her evidence peer reviewed, this will be admissible provided that it meets the
requirements of s18 Evidence Act 2006.
Proven facts and provisional admissibility under s14
Section 25(3) requires that the fact “is or will be proved”. This means that the
expert witness may either state the facts on which the opinion is based during
evidence-in-chief, or give the evidence on the basis that it “will be” proven, ie
that it is provisionally admissible (under s14 of the Evidence Act 2006). As it
is a conditional process, admissibility in such cases will depend on whether
the factual basis of the opinion is indeed proven. If the evidence proving the
factual basis does not eventuate, or if it is insufficient to establish the
admissibility of the expert opinion then the opinion will be disregarded. (In a
jury trial, there will be a direction to rely on the expert opinion only if it finds
the factual basis proven.)
Expert evidence about sanity
Section 25(4) provides for the admissibility of a person’s statement about his
or her state of mind in order to establish the factual basis for the expert’s
opinion on the sanity of that person. It limits its scope to opinions based on
statements made by the person whose sanity is in issue, thereby excluding
statements by others, or statements pertaining to mental disorders falling short
of legal insanity. Furthermore, the statements must be about the person’s state
of mind, and so any statements informing the expert’s opinion made about
other issues will not be covered by s25(4).
The conduct of experts
Expert witnesses should be impartial in their assistance to the court. In R v
Hutton27, the Court of Appeal approved principles similar to those for experts
in civil cases. These principles summarise much of the discussion of s25
above:
* an expert must state his or her qualifications when giving evidence
* the facts, matters and assumptions on which opinions are expressed must
be stated explicitly
* the reasons for opinions given must be stated explicitly
* any literature or other material used or relied on to support opinions must
be referred to by the expert
* the expert must not give opinion evidence outside his or her area of
expertise
* if an expert witness believes that his or her evidence might be incomplete
or inaccurate without some qualification, that qualification must be stated
* an expert has an overriding duty to assist the Court impartially on relevant
matters within the expert’s area of expertise, and
* an expert is not an advocate for any party.
Notice Requirement
The Criminal Disclosure Act 2008 introduced an obligation on the defence to
give notice of expert evidence in criminal proceedings. Section 23 provides
that, if the defendant intends to call an expert witness, he or she must disclose
the brief of evidence or report (or a summary if no brief or report is yet
available) at least 14 days before the date fixed for the trial.
Summary
- The exclusive rules of evidence deal with:
− veracity
− propensity
− hearsay
− opinion
− identification
− improperly obtained evidence. - The Evidence Act 2006 divides what was called “character” evidence at
common law into two classes of evidence:
− “veracity” – a disposition to refrain from lying, and
− “propensity” – a tendency to act in a particular way. - The two criteria for admissibility of hearsay are: reliability; and
unavailability or that “undue expense or delay would be caused”. - In criminal proceedings, a notice of hearsay must be served on the other
party so that each party has sufficient time, prior to the proceeding, to
respond to the statement. - Opinion evidence is not generally accepted; exceptions are contained in ss
24 and 25.
