The nature of the rule
There are a number of rules which govern the evidence procedures in court and in particular there are ones that regulate the examination of witnesses. An example of an established practice is the rule of collateral finality, which applies to cross-examination of all witnesses in court.
The rule provides that the answers of the witness given on replies to questioning under cross-examination on collateral issues are to be taken as final. Therefore, following an answer even if it is incorrect, the party cross-examining cannot attempt to establish the contrary. Essentially they cannot use any further evidence to rebut what the witness has said. This includes either asking further questions or calling other witnesses to testify to the contrary or providing other documentary evidence to the effect.
However, it is important to emphasise that even though such restriction exists, the tribunal of fact is under no obligation to accept the answer given by the witness as true. Therefore, such would still undergo scrutiny by the fact finder in the case.
The reasoning behind the rule is for the courts’ time not to be wasted in establishing all issues even if they are not material to the case. It provides for focus on the essential issues of the proceedings by giving less weight on collateral matters. Further, the rule recognises it would be unfair to ambush a witness with questioning on issues that he had not anticipated.
Meaning of collateral
For the purposes of this rule, collateral issues are ones which are not directly relevant to the facts in issue of the case. In considering whether a matter is relevant to a fact in issue or not, the question to be asked is whether the information is going to the root of an issue in the proceedings.
Collateral issues could be both regarding credibility of a witness as well as establishing factual liability of the party.
Whether the issue is collateral or not is a decision to be made by the judge and it will only be interfered with by the Court of Appeal if it is wrong in principle or was clearly wrong on the facts of the case.
For example when the issue in the case concerns the whereabouts of a person in the evening in question, it would be immaterial to establish whether he took the bus in the morning or walked to work. Therefore, it would be viewed as a collateral issue and the restriction on further cross-examination would apply.
The exceptions of the rule
There are four categories of information which form an exception to the rule of collateral finality. Those are:
Reputation for untruthfulness
Disability affecting reliability
Whenever a question is seeking to examine the witness upon any of the categories above the collateral finality rule would not be applicable. Therefore, the party seeking to establish the relevant facts would be able to produce any evidence available to contradict the answers of the person giving live testimony.
Section 6 of the Criminal Procedure Act 1865, which is applicable to both criminal and civil cases, establishes that where a witness answers questions put to him while giving evidence denies having a previous conviction or refuses to answer such a question, he could be cross-examined upon that conviction.
In dealing with this exception, it is important to bear in mind restrictions on using spent convictions in court. In civil proceedings it is generally not allowed for those to be referred to in the course of the trial. Further, it is strongly recommended for spent convictions not to be mentioned in criminal trials.
Where a witness denies a suggestion of bias or partiality during cross-examination, then evidence to contradict that statement may be called to show that he is prejudiced.
In practice, this rule is commonly used as in many cases it is material to establish motive to support or negate certain evidence.
Evidence of reputation to be untruthful
Evidence is admissible that a witness called by one’s opponent bears such a general reputation for untruthfulness that he is unworthy of belief.
This exception is less popular in practice than the other ones in particular since there are other provisions regulating the use of bad character of witnesses in the course of the proceedings.
Evidence of disability affecting reliability
Under this exception, medical evidence is admissible to show that a witness suffers from a physical or mental disability that affects the reliability of his evidence.
The evidence is not restricted to a general opinion of the unreliability of the witness in the particular circumstances. It may extend further to include evidence of the foundations of the diagnosis and the extent to which the credibility of the witness could be affected.