Similarly we are told that, although the police service may contain the odd bad apple, any endemic corruption that may have been present in the past has now been eradicated. But only a few weeks ago a judge threatened 20 detectives from the South East Regional Crime Squad with contempt proceedings after a drugs case collapsed because of the destruction of evidence.
Moreover, the West Midlands Drug Squad is currently under investigation following allegations that its members have "mislaid" drugs seized in squad operations. And the Chief Constable of West Midlands police, Edward Crew, declared only last week that there are officers working in his force who "wouldn't be employed by Sainsbury's".
The Police Complaints Authority (PCA) has called for a number of changes to be made in the way that specialist police units are staffed and managed. These include the suggestion that the personnel of specialist squads should be rotated regularly so that they do not form too cosy a relationship with the criminals whom they are supposed to be catching. The PCA also suggests that more effective, "hands-on" management is required, accompanied by changes in the Police discipline code.
It is to be hoped that the Home Office will at last act on these recommendations. For example, it is well known that many officers facing severe disciplinary charges manage to escape them (with their pension intact) simply by retiring on medical grounds. Few civilian employees in such a situation have a similar "get-out" available to them and, indeed, this loophole has been criticised by the PCA in virtually every one of its annual reports, ever since it was set up in 1984.
Furthermore, although discipline is an internal civil matter, police officers can be disciplined only if a charge can be proven beyond reasonable doubt - the standard required by the criminal law. The Court of Appeal expressed misgivings about this as long ago as 1985. And in 1990 Sir Peter Imbert, then commissioner of the Metropolitan Police, agreed in a Panorama interview: "Some officers hide behind the system, and that is inevitable ... we have got to see how the system can be changed."
In 1991 the independent inquiry into the working practices of the West Midlands Serious Crime Squad recommended that the police be brought into line with those in civilian employment, where an employer may take disciplinary action if satisfied that an allegation has been proven "on the balance of probabilities" (ie that it is more likely to be true than false). The inquiry recommended, too, that police officers be given, for the first time, the protection of the law on unfair dismissal.
Neither recommendation was acted upon. Both are now being repeated by the PCA, whilst Edward Crew has said that if they had already been implemented "officers ... who should not be police officers ... would not be working".
But it is the complacency of the police and Home Office over the operation of specialist police units which is, perhaps, most offensive. Everyone in the country is aware of the number of miscarriages of justice perpetrated on the basis of evidence generated by the activities of the West Midlands Serious Crime Squad. Yet its disbandment remains the only action apparently taken throughout the police service to ensure that nothing similar could happen again.
But the Serious Crime Squad did not go off the rails because of the recruitment of some evil policemen. On the contrary, there were a number of structural factors which combined to allow the squad to become a "force within a force". The District Auditor found, for example, that senior officers played an unusually active role in operational activities rather than concentrating on providing effective supervision and leadership. As a result, much supervision was "paper supervision", whilst "key managers got no training in management".
At the same time the squad came to see itself as an elite unit boasting a machismo culture in which officers served for many years - one for as long as 16 years - and were able informally to veto new recruits. Indeed, the squad never recruited either a female officer or an officer from an ethnic minority, but drew primarily from those serving in the No 4 Regional Crime Squad, with which it organised many joint operations. It was an officer from this Regional Crime Squad who was responsible for the fabricated confession in the tragic Carl Bridgewater case; and, indeed, he later became one of the Serious Crime Squad's most notorious members.
The episode concerning the South East Regional Crime Squad suggests that these lessons have still not been learnt. The independent inquiry recommended that no officer should serve in a specialist squad for longer than two years except in the case of officers serving in child liaison and fraud squads which require special skills which take some time to develop. Even then it recommended a maximum term of five years. It also recommended that a period of at least two years should elapse before officers should be permitted to return to a specialist squad.
Specialist units within the police can perform a very useful role if their activities are properly managed and if regular checks are made to ensure that they do not duplicate the work of officers on division nor end up investigating offences for which they were not originally set up. When such checks are not put in place, however, these squads have shown an alarming tendency to get involved in "truly infamous conduct". Indeed, that phrase is taken from the report of the Tribunal of Inquiry into allegations of abuse by the Sheffield Crime Squad published as long ago as 1963. It is therefore to be hoped that the latest call from the PCA for changes to be made will not go yet again unheeded.
The writer is a lecturer in law at the University of Birmingham and author of `Unsafe and Unsatisfactory?', the report of the independent inquiry into the working practices of the West Midlands Serious Crime Squad.