Lawyers say Mr Justice Popplewell's decision is an important step towards creating an independent and effective system for handling allegations of misconduct by officers.
The judge had been asked whether it was legitimate for police to use evidence obtained during an investigation of complaints to defend court actions. Victims of police malpractice often claim damages in the civil courts as well as making a complaint to the Police Complaints Authority. Chief Constables order officers to interview the complainant, but then show a transcript to their own lawyers preparing for the court case.
Mr Justice Popplewell said the practice was unacceptable as it prevented alleged victims from co-operating with the PCA and hampered disciplinary proceedings against officers.
'The inquiry is likely to be seriously handicapped, if not rendered valueless, by reason of the fact that a complainant is naturally and rightly unwilling to make a statement which may be used to his disadvantage in the civil proceedings,' he said.
'If a complainant or witness is made more reluctant to come forward because of apprehension about the use of the statement in other proceedings, the whole purpose of the investigation would be emasculated and frustrated.'
His ruling, made earlier this month, is certain to be challenged by the police, who say it will be impossible to implement. Lawyers say the case is likely to go to the House of Lords.
The judgment arose out of a claim brought by Kelvin Wiley, who was charged with armed robbery by the West Midlands Serious Crimes Squad in May 1987. He was acquitted after saying that his confession and other evidence had been fabricated.
Mr Wiley made a complaint to the PCA and sued the police. He refused, however, to be interviewed about his complaint, saying he feared that his statement would be shown to police lawyers defending the damages claim. The PCA was forced to call off its investigation.
Mr Justice Popplewell's decision was described as 'very important' by the PCA, which had voiced concern before about the practice of using evidence from the complaints system.
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