The complexity of the 60-word caution, which the Government plans to introduce in March, is likely to be used by lawyers to argue that their clients were confused and misled, according to a fellow at Oxford University.
A spokeswoman for the Police Federation, which represents rank and file officers, yesterday admitted officers were concerned about the legal implications of having such a wordy caution. The Law Society, which represents solicitors in England and Wales, estimated the new caution would cost an extra pounds 46m a year in additional legal advice and longer trials.
Civil rights groups and opposition parties have already condemned it as a complex tongue- twister that is likely to put vulnerable people at risk while having little impact on professional criminals and terrorists.
Currently, a police officer must tell all suspects: 'You do not have to say anything unless you wish to do so, but what you say may be given in evidence.'
The new caution will read: 'You do not have to say anything. But if you do not mention now something which you later use in your defence the court may decide that your failure to mention it now strengthens the case against you. A record will be made of anything you say and it may be given in evidence if you are brought to trial.'
The changes, if accepted after consultation, take into account provisions in the Criminal Justice and Public Order Bill which allow judges and lawyers to draw inferences - almost certainly unfavourable - from a suspect remaining silent. The expanded caution is intended to ensure that everyone is aware of the possible implications of refusing to speak.
Adrian Zuckerman of Oxford University, a Law Fellow who specialises in criminal evidence, said: 'The proposed changes will undoubtedly lead to numerous legal battles. Defence lawyers are bound to make the point that when the caution was given, it was confusing and therefore no conclusions or inference can be drawn from any silence.'
Roger Ede, secretary to the criminal law committee at the Law Society, predicted that very few police officers would understand the implications of the new caution and certainly most members of the public would be completely baffled. It will become a 'legal minefield,' he said. 'The attempt in the amended caution to set out the legal position demonstrates the unworkability of the new laws. If any suspect asks a policeman what it means I'm sure most would not be able to answer.'
The spokeswoman for the Police Federation said: 'We accept the new cautioning is a bit of a mouthful but we are very pleased that the prosecution can challenge a defendant who choses to remain silent at the time of arrest. However, we acknowledge that the length and complexity of the caution may cause some confusion.'
Leading article, page 10