- . Some prisoners were released the day after Booth was decided.
- . Others will be released as soon as inspection of their files reveals that they should be released under Booth.
- . Other prisoners will have their release dates re-calculated in compliance with Booth.
- . And some prisoners have served their sentences under the law as it had previously been understood to have been, but if Booth had been applied to them they would have been released earlier.
That seems to me to be the legal answer. The policy answer will depend on the weight to be given to finality in litigation as against the need to ensure that those who enforce the law obey the law, particularly in relation to people - prisoners - who are otherwise without remedy against institutional abuse of power. Their vulnerability became entrenched at a time when the final appeal court - the Privy Council - was, as a matter of practicality, out of their reach. I think the policy answer will be consistent with the legal answer, that retrospective effect of Booth will be acknowledged, and that compensation should be paid. There will still be arguments about whether compensation can be given without discriminating in favour of those prisoners whose offences did not have victims, because of the Prisoners' and Victims' Claims Act 2005.
Update: On 18 December 2017 the Court of Appeal, upholding the High Court, held that the decision in Booth, like the great majority of common law decisions, is retrospective in effect, and that the prisoners who had not been released on their correctly calculated dates were falsely imprisoned and were eligible for damages, and that an appropriate award for a recidivist prisoner who was not freshly traumatised by incarceration was in the range of $8,000 to $12,000 for one month's wrongful imprisonment: Chief Executive of the Department of Corrections v Gardiner  NZCA 608.