Keith Ng of On Point has posted an excellent interview with a lawyer on the admissibility of prior convictions or evidence of past wrongdoing in court.
View the whole post here
Under what circumstances are prior convictions inadmissible as evidence?
Evidence of prior bad acts, whether they resulted in conviction or not, are generally inadmissible. Your average jury will never get to hear about a defendant’s list of previous convictions, no matter how long it may be.
Does the prosecution generally try to get prior convictions admitted?
I don’t have detailed statistics, but the prosecution would hardly ever seek to have such evidence admitted. The likelihood that they are going to win any application to have such evidence admitted is very low.
There are two basic situations when the prosecution will seek to adduce evidence relating to a defendants prior actions.
First, the more likely of the options, is when a defendant gives evidence on their own behalf (which most don’t). If a defendant is giving evidence and says, ‘I’m a good person, I’d never burgle someone’s home’ and the prosecution know he’s got previous convictions for burglary, they’re then allowed to question him about it.
If a defendant chooses to put his good character into evidence, then the prosecution can put his bad character into evidence to even things out. Knowledge of this is a major reason why defendants rarely give evidence on their own behalf.
The second situation would be substantially rarer. In situations where the defendant is charged with [offending that] is strikingly similar to [something that] the offender has been convicted [of], the prosecution can apply to the court to be able to admit it. A classic example of such a striking similarity is the English case of Boardman – an accused charged with a burglary in which the offender left at the scene an esoteric symbol written in lipstick on a mirror and it can be shown that in all the accused’s prior burglaries he had left the same marking.