A boy emerges from care with no qualifications. Several years later, he is sent to jail. As an adult, it turns out that he may have been abused while he was in a home - one of the factors which perhaps contributed to his antisocial behaviour and in turn has led to his prison sentence. When he makes an official complaint, it is his word against that of the professional he has accused. His time inside makes him a discreditable witness. So how is justice to be achieved?

Flip the coin and there is an equally difficult dilemma. A carer is visited by three young men, whom he knew as children. If he doesn't pay up, they will report a false case of abuse. They may report him anyway in the hope of receiving compensation. It is the carer's word against three, whom will the jury believe?

The answer in both cases, of course, is that the guilty should be convicted and the innocent set free. First, however, a meticulous mass of evidence has to be accumulated, a challenge made difficult because when these adults were young the complaints of children were barely heard in the care system, never mind recorded.

The records are sparse, especially in homes where abusers have subsequently admitted to years of assaults. So testimony is often all there is. But good detective work still should be able to correlate patterns of abuse or reveal inconsistencies that may make the charges untenable. Good detective work, however, has not, apparently, always been undertaken.

More than 100 cases of carers and teachers who have been convicted of child abuse are to be investigated by the Criminal Cases Review Commission and the Historical Abuse Appeal Panel.

The review has been triggered by concern over alleged police tactics, including trawling for information, and lawyers peddling for business, promising large sums of dosh in compensation. The commission says: "With very little corroboration, one person's view [may have been] taken against another's."

If true, that is a stain on the police and the judiciary. The issue of compensation should also be addressed to see whether the prospect of a pay-out lures some into corrupting the system at the expense of others genuinely seeking justice.

Of course, no one should be locked up unfairly. But reviews should be undertaken with a sense of balance, not triggered by a state of panic. Otherwise, there is a genuine risk that the guilty not only go free, but they emerge from prison as martyrs.