Evidence is often given that the defendant made an admission or confession of guilt. The evidence may be of a conversation in which the defendant verbally confessed or it may be a written record of questions asked by a police officer and answers given by the defendant (a record of interview). For a confession to be admissible in evidence, it must be made freely and voluntarily.

There is also the requirement that the police officers comply with Section 74D of the Summary Offences Act 1953 (SA) , recording the interview with suspects [see generally the obligations on recording interview at ss 74C-74G].

Any interview will not be admitted if it was induced by a threat, promise or untrue representation made by the police or some person in authority. The defence may object to the admissibility of a record of interview on this ground and the court will consider whether to admit it or not.

Even if a court decides that a confession is voluntary, it may be excluded if it would be unfair to the defendant to admit it. A court may also exclude a confession on the grounds of public policy. This means weighing the public interest in having offenders convicted, against the public interest in discouraging police officers from engaging in unlawful conduct during the investigation of a crime.

The High Court of Australia in Nguyen v The Queen[HCA] 2020 held that prosecution's obligation to put a case fully and fairly requires tender of records of interview containing mixed statements (inculpatory and exculpatory statements). The prosecution's obligation of fairness in the conduct of a trial requires the tender of mixed statements unless there are good reasons not to do so. Where the reliability or credibility of the evidence is demonstrably lacking, the prosecutor may be justified in refusing to tender such evidence.