Principles which apply to the giving of evidence in proceedings in a court.
For example, evidence may be excluded if it has nothing to do with the case, would distract the minds of the jury from the real issues of the case, is unreliable, would be unduly prejudicial to the defendant, or was untruly or illegally obtained. Hearsay evidence is normally not allowed.
The admissibility of evidence is a question of law which the judge decides, removing the jury while he/she hears the evidence in dispute to see if it may be used in the case.
In NSW, the procedural rules and rules of admissibility relating to specific classes of evidence are outlined in the Evidence Act 1995 (NSW).