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Understanding Covert Surveillance: Human Rights Defence and Privacy Laws

Author: Azizur Rahman  2 May 2012
4 min read

It is now common-knowledge that the police have at their disposal listening device technology, i.e. 'bugs'. In fact the type of technology involved is freely available to the public and the details are even sometimes disclosed to the defence, see e.g. in R v Allsop [2005] EWCA Crim 703, 17/3/05. This type of evidence gathering technique is clearly a valuable asset to the police as it can provide damming evidence and it is now being used more and more in certain types of cases; e.g. large drug conspiracy allegations. In this article we look at some of the evidential issues that should be considered when faced with this type of evidence.

The Authorisations

Authority to place a bug in someone's home or car is required from a Senior Officer and then a Surveillance Commissioner, sections 32-40 of the Regulation of Investigatory Powers Act 2000. Following the recent Court of Appeal cases of R v G.S. and Ors [2005] EWCA 887, unrep. 22/4/05, para 35 and R v Allsop, para. 26 it will now be more difficult for the defence to demand the applications and authorisation forms. These were often disclosed prior to an argument that the device was placed unlawfully. Now the Court of Appeal has made it clear that the Act provides all the relevant lawfulness safeguards and if there is a challenge all the Crown have to do is produce the relevant authorisations to the Judge for his inspection. In any event the latest case-law is helping to ensure that those lawfulness challenges will only be successful in a very limited number of cases, see e.g.; R v Button [2005] EWCA Crim 516, 4/3/05.


This can be a difficult area and there may still be scope for challenge where a Defendant insists that he is not the speaker identified on the transcripts as uttering the damming words. Suppose, for example, a bug is placed in a house or car and the police then listen and transcribe weeks or months of conversations without actually keeping observations on the car or house for the whole of that period, not an unusual scenario. Sometimes the voice attribution may be painfully obvious - for example where the speaker the police are interested in is clearly identifying himself. But what about where there are a number of speakers and no visual I.D. or obvious reference of who was actually present? In such a case the Crown may produce transcripts saying that 'Speaker 1 is X'. X may disagree. How do the Crown prove their case? The usual route is for a voice identification expert to listen to the disputed tape. However, this is not the end of the story. First of all identification by voice is not like identification by DNA or fingerprint - it is not an exact science. The Crown's expert is expressing his or her opinion and a defence expert may come to a different opinion. Also, there are two types of voice analysis that the experts commonly use. One is more reliable than the other, so it is worthwhile understanding what technique has been used. There is the auditory technique which involves the expert listening to the sample and the disputed tracks and making identifications through features such as dialect or accent. Then there is the more scientific acoustic method which involves the use of on screen display of information about the acoustic properties of the speech which depend upon the individual's vocal tract, mouth and throat.

In R v O'Doherty [2203] 1 Cr. App. R 5 the Northern Ireland Court of Appeal held that in the present state of scientific knowledge no prosecution should be brought where the identification evidence relied solely on the auditory method. An exception to this rule might be where the police know that X is present in a car, or a room full of people, and the expert is simply being asked to listen to the voices and attribute X to one of the speakers. The issue then becomes 'how do the police know that X was present'. The authors are likely to be involved soon in appeal on this very point where the 'knowledge' was said to come from the limited context of what was said rather than a visual identification in an auditory analysis case. Given the special status of identification evidence of any sort it may be argued that the use of the auditory method alone should be in relation only to true visual attribution cases.

The Sample

Another area of challenge which the authors are to be involved in is the use of police interview tapes as a reference sample for the Crown's voice expert. Both Article 6 of the European Convention and, arguably our own trusted police caution, make it clear that there remains a right to silence - a right not to incriminate oneself. By speaking in a police interview you maybe contributing to the police case against you if the police, as likely, have not warned you that there exists covert tapes. This is because you have unwittingly provided the police with the sample they need for their expert analysis. In a case called Allen v UK (2003) 36 EHRR 12 a suspect in a murder enquiry chose to remain silent in his police interview. The police got round this by placing an informant in his cell who was 'wired for sound' and who promptly badgered evidence out of him which was recorded and used to convict him. The Strasbourg Court held that that was a breach of the right not to incriminate oneself which is "primarily concerned with respecting the will of an accused person to remain silent." The authors are applying the same principle to the use of the interview tape. Watch this space.


Jonathan Lennon is a Barrister specialising in criminal defence and Prison Law at 23 Essex Street Chambers in London. He is co-editor of the Prison Law Reports.

Aziz Rahman is a Solicitor - Advocate and Partner at the leading Criminal Defence firm Rahman Ravelli Solicitors, specialising in Human Rights, Financial Crime and Large Scale Conspiracies/Serious crime. Rahman Ravelli are members of the Specialist Fraud Panel.

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Aziz Rahman is Senior Partner at Rahman Ravelli and its founder. His ability to coordinate national, international and multi-agency defences has led to success in some of the most significant corporate crime cases of this century and top rankings in international legal guides. He is recognised worldwide as one of the most capable legal experts regarding top-level, high-value commercial and financial disputes.

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