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Discretion to Exclude Evidence: Bunning v Cross

When evidence against an accused person has been obtained in a way that did not comply with procedural rules, the court may be asked to exercise its discretion to exclude the evidence. This may occur where a police interview was carried out without the proper caution, where police searched a property without a warrant or where the search went beyond the scope of the warrant.

In this situation, the defence may argue that the relevant piece of evidence was obtained improperly and ought to be excluded from the proceedings. The court will then be required to consider whether to exercise its discretion to exclude the evidence. The discretion to exclude evidence improperly obtained is known as the Bunning v Cross discretion.

Bunning v Cross

IN 1978, the  High Court decision of Bunning v Cross dealt with when courts should exercise their discretion to exclude evidence that has been improperly obtained. In that case, Western Australian police had stopped a man who was driving erratically and speeding. The patrolman smelt alcohol on the man’s breath and asked him to get out of the car, which he did, with some difficulty. The patrolman asked the driver if he had been drinking and he told him that he had had about three beers. The patrolman did not ask the driver to do a preliminary breath test but asked the driver to come back to the police station with him. There the driver was breath tested and recorded a BAC of 0.190.

The decision at first instance

The driver in Bunning v Cross was charged with speeding and driving under the influence of alcohol. In the Perth Court of Petty Sessions, he was found guilty of speeding, but the charge of driving under the influence was dismissed due to the magistrate finding that evidence of the breath test was inadmissible. This finding was based on the fact that the patrolman had had no objectively reasonable suspicion that the driver was affected by alcohol before administering the breath test. This was because the police had failed to administer an on-the-spot breath test, as required under the WA Road Traffic Act 1974.


The prosecutor obtained an order to have the Supreme Court review the decision. It found that the magistrate had erred in ruling the evidence inadmissible. Rather, it said, there was a discretion for the magistrate to exclude the evidence based on the finding that it was improperly obtained. The Supreme Court remitted the matter back to the magistrate, who exercised the court’s discretion to exclude the evidence. He then dismissed the charge.

After the matter had been through a number of other procedural steps, it came before the High Court, which found that the Magistrate had exercised his discretion to exclude the evidence correctly.

Discretion to exclude evidence

The High Court found that the discretion to exclude evidence improperly obtained can rightly be exercised where the unfairness to the defendant if the evidence were admitted, outweighs the public interest in obtaining evidence to aid the enforcement of the law. Courts may also exercise their discretion to exclude evidence where the extent to which the evidence would prejudice a fair trial outweighs the probative value of the evidence.

The High Court found that there was no room for the exercise of the discretion to exclude the evidence of the breath test result in the matter of Bunning v Cross. This was because what occurred, in that case, did not involve unfairness to the accused but was unlawful only because the patrolman wrongly believed he was entitled to take the driver back to the police station without first conducting an on-the-spot breath test. There was no deliberate disregard of the law. Furthermore, the nature of the illegality did not have a bearing on the cogency of the evidence that was subsequently obtained and the offence being investigated was a relatively serious and prevalent offence. The High Court stated that the magistrate did not appear to have considered any of these criteria or to have given any weight to the public interest of convicting persons who commit offences.

Excluding evidence improperly obtained

When a person is charged with a criminal offence and it appears that some of the evidence the police are relying on may have been improperly obtained, the defence should seek that the matter be listed for a voir dire.

A voir dire is a pre-trial proceeding where the admissibility or inadmissibility of an item of evidence is determined after submissions from defence and prosecution. Where the defence is seeking to have evidence that is prima facie admissible excluded from the trial, it bears the onus of establishing that the evidence ought to be excluded. This can be achieved by persuading the court to exercise the Bunning v Cross discretion. Where the prosecution is seeking to have evidence admitted that is prima facie inadmissible, it bears the onus of establishing that the evidence should be admitted.

If you require legal advice or representation in a criminal matter or in any other legal matter, please contact Armstrong Legal.

Fernanda Dahlstrom

This article was written by Fernanda Dahlstrom

Fernanda Dahlstrom has a Bachelor of Laws, a Bachelor of Arts and a Graduate Diploma in Legal Practice. She has also completed a Master’s in Writing and Literature. Fernanda practised law for eight years, working in criminal defence, child protection and domestic violence law in the Northern Territory and in family law in Queensland.

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