The defendant cannot be forced to give evidence and can choose whether to do so or not. A defendant who decides to give evidence does so by going into the witness box, taking the oath (or affirming) and answering any questions asked first by the defendant's lawyer and then by the prosecutor in cross-examination. The defendant may also call witnesses who are able to give evidence relevant to the defence.

There are a number of different defences available to a defendant and common defences are discussed below. If appropriate, a defendant may rely on more than one defence as alternative defences, but must be careful not to prejudice a good defence by throwing in weaker or conflicting ones.