Generally, the prosecution cannot ask questions of a defendant which tend to show that the defendant has a bad character or has committed other offences. However, if at the trial the defendant or the defendant's lawyer tries to attack the credibility of a prosecution witness by reference to bad conduct by that witness, the court may also allow the defendant (if she or he gives evidence) to be questioned about her or his own bad character or conduct.
The defendant is entitled to raise her or his good character as an issue at the trial and to have that evidence taken into account on the question of guilt or innocence. In this case, however, the prosecution can call evidence to rebut this to show that the defendant is of bad character.
At the trial, the decision whether to attack the character of prosecution witnesses or whether to raise the good character of the defendant needs careful consideration.