West Yorkshire Police said the way officers secretly gathered evidence against Keith Hall was approved by the Crown Prosecution Service before he was charged with the murder of his wife, Patricia. But Mr Hall was acquitted on Thursday after a judge said that his taped 'confession' was inadmissible as evidence.
Leeds Crown Court was told that Mr Hall, 38, fell in love with an undercover police officer called 'Liz', who had replied to a lonely hearts advertisement. During a date with Mr Hall, she recorded a conversation in which he is heard saying he strangled his wife and burnt her body. The body has never been found.
But during the week-long hearing, Mr Justice Waterhouse accepted legal argument that the way the 'confession' was extracted breached the Police and Criminal Evidence Act (PACE). The jury was unaware of the tape until after it returned its not-guilty verdict and the judge had released a full transcript.
Detective Chief Superintendent Michael Woodhouse said: 'It is not for police to question the decision of the jury. There are no plans for the case to be reopened. The police were placed in the position of seeking the truth, and throughout the investigation they fully consulted the Crown Prosecution Service.'
Officers within the force said privately that they were desperately disappointed by the judge's decision.
There have been several cases in which the Court of Appeal has upheld the police's right to use evidence gathered by entrapment or in a clandestine way. But the issue becomes difficult when undercover officers question a suspect, rather than simply playing a role and partaking in what would appear to be a natural conversation.
Roger Ede, secretary of the Law Society's criminal law committee, said the codes of practice for the detention, treatment and questioning of suspects under PACE state that when there are grounds to suspect an offence has been committed by a person, they must be cautioned before being questioned.
'The general principle in English law is that a person need not answer any questions or provide information that might incriminate him,' he said. 'That is the whole purpose of a caution. The judge was right not to have allowed this evidence because the suspect was not cautioned.'
Several times in the transcript it is clear that the undercover officer asked questions which led to Mr Hall incriminating himself.
Dr Andrew Choo, lecturer in law at Leicester University, said Mr Justice Waterhouse would have had no room for discretion if he considered the confession had been gathered unreliably under PACE.
'The whole area is a minefield because evidence can be excluded automatically - when it is unreliable or gathered in an oppressive way - or at a judge's discretion,' he said. 'Unfortunately, the English courts are unwilling to lay down more guidelines.'
West Yorkshire Police continued to keep the female police officer's identity a secret yesterday. A colleague said: 'There will be no chance of 'Liz' bumping into Mr Hall in the street.' Mr Hall continues to deny killing his wife and has appealed for her to get in touch with him. He was said yesterday to be negotiating to sell his story to a Sunday newspaper.Reuse content