Short of having a well-heeled campaigning guardian angel (a la Joe Karam), or tissue samples taken and retained (not always a given) which might be tested by new DNA methods and which then show innocence, or of finding a rich and powerful law school with professors and students willing to run an Innocence Project (as with some parts of the US), what prospect do the estimated 20 or so New Zealand "victims" of miscarriages of justice, at any one time wrongfully languishing in our prisons, have of proving their miscarriages and being set free?

Virtually none, regrettably.

The majority of these persons wrongfully imprisoned will come from the most disadvantaged sections of our nation. They will not be white persons from middle-class families, who might well attract supporters and campaigners.

David Bain was fortunate. The other 19 or so wrongfully inside will not be so fortunate. The figure of 20 comes from work done by a retired High Court judge, Sir Thomas Thorp, who published a paper on miscarriages of justice in New Zealand some three years ago.

A long-serving judge and before that a Crown Solicitor, he had carried out studies after having been officially commissioned to look into some claims of miscarriages.

Sir Thomas reached his estimate of 20 wrongfully imprisoned by looking in depth at figures that had emerged from England and Scotland - over a 10 year period - since the setting up in those countries of bodies called Criminal Cases Review Commissions. Over that time a consistent error/miscarriage rate was found and, given the similarities of our systems with theirs, the British figures were extrapolated by Sir Thomas to reach his calculation of 20 persons wrongly in jail at any one time.

Following the disasters that emerged in England as to the way wrongful convictions had been obtained and upheld on appeal in certain Northern Ireland cases, a review commission was started up in England, Wales and Northern Ireland in 1997, to review convictions claimed to have been wrongly obtained.

The commission was given wide-ranging powers to make the fullest of factual inquiries because it was believed that the British criminal appellate system was too constrained and narrow and therefore not an appropriate instrument, or indeed available instrument, to use to try to perceive let alone rectify miscarriages.

In the 10 years or so since its inception the commission has overturned, or taken steps leading to the overturning of, more than 200 wrongful convictions. And with results being achieved in a relatively short time frame. No more extended marathons like the Bain saga has been here - a decade and a half ...