Applications by the police for search warrants are, necessarily, made without notice to the suspect whose home or offices are to be searched. One consequence of this is that the police are under a duty to make full disclosure to the magistrate or Crown Court judge – as it was put by Lord Justice Bingham (as he then was) in R v Crown Court at Lewes (1991) 93 Cr. App. R 60 “[The] judge must be told anything to the knowledge of the party applying which might weigh against the making of the order”. However, as illustrated by the recent decision on the Court of Appeal in R v Zinga and Pillai [2012] EWCA Crim 2357, failure to comply with that strict duty does not mean that the application will be held to be unlawful – with the (unintended) consequence that the police are in effect given licence not to comply with their duty.

In Zinga and Pillai the defendants were prosecuted by Virgin Media Limited for offences arising out of the unlawful use of set top boxes which allowed users to watch programmes offered by Virgin on subscription channels without payment of Virgin’s fees. Both men were convicted of conspiracy to defraud and sentenced to very substantial periods of imprisonment. As part of its investigation leading up the prosecution, Virgin had enlisted the assistance of the Metropolitan Police who were persuaded to apply for and obtain search warrants. On an appeal against conviction, the sole issue was whether the grant of the warrants had been unlawful by reason of non disclosure at the warrant application to the magistrate – neither the police officer who made the application, nor a representative of Virgin who was present at the hearing told the magistrate that the proposed prosecution was to be brought by Virgin as a private prosecutor.

The Court of Appeal was clear that this was something that should have been disclosed - Lady Justice Rafferty expressed this in trenchant terms: “ We do not understand why it was felt acceptable, during an ex parte application with its duty of full disclosure, to keep from the Bench that a private prosecution was expected. We would wish to emphasise that the obligation on an applicant for a warrant is the same as that imposed on any person making an application to a court, namely one of ‘full and frank disclosure’”. The Court of Appeal also found that if this had been disclosed the magistrate hearing the warrant application might have “probed” the reason why the CPS was not bringing the prosecution and might have gone to ask additional questions. Nevertheless, it was held that the search warrants should not be quashed, because it had not been shown by Mr Zinga and Mr Pillai that the warrants would not have been granted if full disclosure had been made.

There have been a number of conflicting decisions about the test to be applied when considering the consequence of a failure in disclosure: whether it is that the non disclosure might have made a difference to the grant of the warrant or whether it is that it would in fact have made a difference. These authorities were considered by the Divisional Court in the recent Tchenguiz brothers’ challenge against the SFO. On the facts of that case it did not matter which test applied since non disclosure, combined with other errors, meant that the warrants would not have been granted even if the application had been properly made, but the Court went on to comment, without reaching a concluded view, that the authorities and the public interest “point” to the test being whether in fact full disclosure would have made a difference to the decsion to grant the warrants. In Zinga and Pillai the Court of Appeal adopted this without considering the slightly provisonal nature of the Divisional Court’s conclusion.

The “would have made a difference” test presents a very high threshold. Although there are good policy reasons for ensuring that technical breaches do not result in warrants being set aside – and this was shown in Zinga and Pillai itself, where significant evidence was obtained as result of the execution of the search warrants – there is a very real concern that in setting the bar this high, the practical effect will be that police officers will take a restrictive view of their duty of disclosure, comforted by the knowledge that the risk of adverse consequence, even if a Court subsequently concludes that they were in breach of that duty, is small.