I have no doubt that for many people the suggestion that some of the 29,000 people in jail in Australia may in fact be innocent will be met with considerable scepticism if not ridicule. Surely, it might be argued that with the very high standard of proof required by our courts, strict rules defining what types of evidence are admitted in court, and reasonable opportunities for appeal after conviction, the possibility of error in the criminal justice system must be very low.
As in all other areas of human behaviour, mistakes are sometimes made by the police, prosecutors and the courts, as a result of which innocent people find themselves on the receiving end of the penal system. The tantalising question is: How often does this occur?
Is it just a trivial number, or is it as high as 2 or 3 per cent of all those behind bars, as some commentators have claimed? If the figure was in the latter range it would mean that between 480 and 870 people are wrongly in jail.
Experts with extensive experience in this field in Australia are generally reluctant to make an estimate as the exact proportion of cases resulting in wrongful conviction cannot be accurately determined. However, estimates from other countries range between 1 and 10 per cent, clustering around 5 per cent.
We certainly know that the answer is not zero, as from time to time cases come to public notice where a prisoner is released from jail after it was established (perhaps by DNA or other forensic evidence) that he or she could not have committed the offence. It may be a false impression, but it seems that a disproportionate number of cases like this have come to light in Western Australia.
There are a number of different ways in which miscarriages of justice can occur. It may be simply a matter of an eyewitness who, without malice, makes a false identification. It is well known that evidence of identification is notoriously unreliable. At a more sinister level, it is possible that in some cases, two or more potential witnesses may conspire to give false evidence that will ensure that the accused person is convicted.
The most serious cause of false convictions stems from the actions of police themselves. There are no doubt many cases in which the police know that a suspected offender is guilty but they also know that there is not sufficient credible evidence for a conviction to be obtained. In cases like this, some police have been known to resort to either or both of two illegal practices known colloquially as ''verballing'' and ''planting''.
Examples of these practices are cases in which police swear in court that the accused person made an informal confession when he was arrested, or placed illegal drugs or a weapon on or near the accused person in such a way that other police or prosecutors gain a clear impression of guilt in the accused person. These and similar practices (we may assume that torture is no longer used at least in this country) are named by moral philosophers as ''noble cause corruption''.
It is not difficult to understand why police officers occasionally resort to practices which fall under this heading. For example, if the accused person is a well-known offender who has caused considerable harm and distress in the community but is unlikely to be convicted because the evidence against him or her is not absolutely watertight, the police handling the case may feel that they are only doing what is necessary to protect the community. Their cause may be noble, but these methods are corrupt and always unacceptable.
As with the extent of wrongful convictions, it is impossible to know how extensive is the use of noble cause corruption by police. It is possible that it has largely been eliminated by more thorough internal supervision of police practices, but that may just be wishful thinking. A number of former police in different jurisdictions, including the ACT, have told me that it has certainly taken place in the past.
All of this paints a scenario which should be a cause of great concern to the law-abiding community. We can hardly be proud of the fact that significant numbers of people in jail are really innocent, and that in at least some of these cases the problem was caused by the police themselves.
But there is some good news that might provide some hope for the future.
The hope stems from the fact that both in Australia and overseas more people are starting to talk about the problem of wrongful convictions and doing something about it. In recent years a number of law schools in different universities have established Innocence Projects which, together with some volunteer lawyers, encourage law students to investigate wrongful convictions and perhaps initiate appeals or reviews of relevant cases. Griffith University in Queensland is currently leading this work.
There is even an Australian Innocence Network which has the ambitious aim, among other aims, ''to prevent, expose, correct and educate the public on wrongful conviction and other types of injustice within the criminal justice system''.
The Australian network also works closely with an international innocence network which currently has 20 or more nations as members. Of this group, the Americans have been the most active over many years, possibly because the need is greater there than in many other countries.
Over and above what can be done by university staff and students and practising lawyers giving their time to this work, there is a need for action at the level of governments. In Britain a Criminal Cases Review Commission has operated for the past 14 years. It is understood that a similar body is under consideration by the South Australian Government. Other states should do the same, but ultimately the Federal Government should take an interest in this subject. It is an issue that is central to the way we are seen around the world.
David Biles is a Canberra consultant criminologist.