[note 8/6/09: This article has been heavily amended. It appears the Herald may have published information in breach of a suppression order, so I have removed all details relating to the matters reported by the Herald]
It has become increasingly common for a controversial acquittal to be followed by the release of "suppressed" evidence.
In the Bain case this was bound to happen. Saturday's Herald contained a report about evidence that was "suppressed".
I'm not going to speculate on whether that evidence would have been critical to either side.
And I've previously made it clear I have no interest in reviewing the evidence to decide whether or not Bain committed mass murder. The jury heard the evidence and made a decision. I respect that decision. But I'm happy to discourse on the relevant law.
So I will talk about one of the most common grounds for refusing to admit evidence in a criminal trial. That is the situation where the Crown wishes to introduce evidence about the past acts, state of mind or convictions of a defendant. This is generally known as "propensity evidence".
What is the law?
So what is the legal basis for using, or not using, evidence of past acts or even prior convictions? It starts with the Evidence Act 2006, which sets out the rules of evidence the courts are required to follow. The courts work with facts, so the rules of evidence are designed to ensure only the most reliable facts are admitted as evidence.
So in many cases the past acts or criminal convictions may be disallowed as evidence, because they fall within the scope of section 43 of the Evidence Act, being evidence offered by the prosecution about a defendant's propensity to act in a particular way or to have a particular state of mind.
Section 43 says:
Why do the rules exist?
(1) The prosecution may offer propensity evidence about a defendant in a criminal proceeding only if the evidence has a probative value in relation to an issue in dispute in the proceeding which outweighs the risk that the evidence may have an unfairly prejudicial effect on the defendant.
(2) When assessing the probative value of propensity evidence, the Judge must take into account the nature of the issue in dispute.
(3) When assessing the probative value of propensity evidence, the Judge may consider, among other matters, the following:
(a) the frequency with which the acts, omissions, events, or circumstances which are the subject of the evidence have occurred:
(b) the connection in time between the acts, omissions, events, or circumstances which are the subject of the evidence and the acts, omissions, events, or circumstances which constitute the offence for which the defendant is being tried:
(c) the extent of the similarity between the acts, omissions, events, or circumstances which are the subject of the evidence and the acts, omissions, events, or circumstances which constitute the offence for which the defendant is being tried:
(d) the number of persons making allegations against the defendant that are the same as, or are similar to, the subject of the offence for which the defendant is being
(e) whether the allegations described in paragraph (d) may be the result of collusion or suggestibility:
(f) the extent to which the acts, omissions, events, or circumstances which are the subject of the evidence and the acts, omissions, events, or circumstances which constitute the offence for which the defendant is being tried are unusual.
(4) When assessing the prejudicial effect of evidence on the defendant, the Judge must consider, among any other matters,—
(a) whether the evidence is likely to unfairly predispose the fact-finder against the defendant; and
(b) whether the fact-finder will tend to give disproportionate weight in reaching a verdict to evidence of other acts or omissions.
So why have these rules? Why not just put all the facts before the jury and let them decide?
The answer is simple. In a criminal trial the defendant is accused of an offence. The fact that the defendant may have said or done something similar in the past is arguably irrelevant to the central question: did he/she do it on this occasion? If the facts of the case do not establish an offence, the defendant's past actions should be irrelevant. Juries are laypeople and don't understand the laws of evidence. Some jurors may put undue weight on someone's past conduct when the facts don't necessarily prove an offence has been committed.
Of course, a propensity to act or think in a certain way may be relevant in some situations. So the judge in a criminal trial has to decide whether to admit the evidence.
The Law Commission reviewed the evidence rules relating to propensity and veracity in 2008, following the controversial Rickard/Shipton/Schollum acquittals. You might recall that in that case the jury were not told that Shipton and Schollum were already serving prison sentences for rape. The Law Commission's report concluded that it was too early to tell whether the relevant provisions of the Evidence Act needed to be changed.
Some people will still say the law is absurd and that the jury should always hear all of the evidence. But remember - a defendant is not on trial for his/her past acts. If it is not directly relevant and may in fact do great harm to the defendant, propensity evidence should not be admitted.