There are many different types of evidence that can be obtained improperly. The three common classes of improper evidence are unreliable confessions, entrapment, and breaches of procedure (unauthorised searches or recordings). A blanket rule of exclusion would require the rejection of all the above evidence types.
An unreliable confession most commonly arises from either intimidation or inducement. That is to say if confession is reached through aggressive questioning or the promise of some incentive (perhaps bail), such a confession would be classed as unreliable. All such confessions are likely to be excluded from evidence as they are unreliable and therefore breach the right to a fair trial and obscure the truth. This unreliability derives directly from the way in which they were obtained.
Entrapment occurs when a police officer poses as an average citizen and induces a person to commit a crime. The major issue is that, without the police officer, the person may have been very unlikely to commit the crime. The common measure by which exclusion is determined is whether the police officer presented an exceptional or unexceptional opportunity for the person to commit the crime. If the former is true the evidence can be excluded as the method used to obtain it may have jeopardised its reliability. Otherwise the court will tend to ignore any defence that is founded upon criticising police behaviour since the reliability of the evidence was unaffected.
Evidence obtained through breaches of procedure tends to be the most commonly accepted form of improperly obtained evidence in english courts but offers the clearest point of contention in the exclusion debate. Breaching procedure will have no direct effect on the reliability of evidence. That said, procedure exists to protect the rights to privacy of an individual. The argument for exclusion of evidence is twofold. Firstly it is argued that unlawfully obtained evidence may breach the right to a fair trial. Secondly it is argued that the police must be discouraged from intentionally breaking procedure. A fine interpretation of the first argument is that impropriety may affect reliability but it is not the impropriety itself that threatens the fairness of the trial. As such, rather than blanket excluding all improperly obtained evidence it can be left to the discretion of the court whether or not each piece of evidence is reliable enough to accept. The second argument fails to appreciate the possibility of punishing breaches without obscuring the truth and risking false acquittals. Consequences can be distributed to the offending officers without rejecting the evidence.
In a ruling at the court of appeal Lord Auld proposed that ‘save in the case of confessions and generally as to evidence obtained from the accused after the commission of the offence there is no discretion to exclude evidence unless its quality was or might have been affected by the way in which it was obtained’. This is an elegant summary of the strongest compromise, that rather than excluding evidence due to its origin, its exclusion should depend on the extent of its reliability.
Contributed by Will Andrews