Thanks to the Official Information Act, I can now confirm that a law change in late 2010, which removed the right to vote from a large number of prisoners sentenced to short terms of imprisonment, has given the right to vote to up to 37 prisoners (as at April 2013) serving life sentences, or preventive detention.
Back in late 2010, at the height of National's attempts at bipartisan consensus for electoral law changes, the National Party, with support from the ACT Party (which spoke against, but voted in favour of the law) passed the Electoral (Disqualification of Sentenced Prisoners) Act over opposition from every other party in Parliament.
Under the old law, people sentenced to three or more years imprisonment lost the right to vote while they are detained. Other prisoners remained entitled to vote. The law extended the ban on voter enrolment to all sentenced prisoners. Thanks to a wonderful blogpost by Andrew Geddis, Parliament avoided accidentally giving the vote to a range of people who were disqualified from voting under the old law, but who through amendments recommended by the select committee (which was trying to avoid the new prohibition being retrospective) would have been required to enrol, and entitled to vote. This included people sentenced to preventive detention, and life sentences. A rather big mistake.
They fixed that up during the committee of the whole - adding a section to the law that says that people who were disqualified from voting immediately before the law took effect were still disqualifies. But, thanks to the magic of the OIA, I can confirm that there is a group of prisoners, who would have been banned from voting if the law hadn't changed, who are now entitled to vote.
There are a couple of points to make clear. Under both the old law, and the new law, as soon as a prisoner is released, they are entitled (actually required) to enrol, and are allowed to vote. This includes people serving short sentences, right up to those serving life sentences or preventive detention.
This means that people who were sentenced before 16 December 2010 (when the disqualification law took effect), but who were out at that time, were entitled to vote (assuming they met the other qualifications: NZ citizen or permanent resident, at least 18 etc.) when the law took effect.
Which is important, because as I note above, the fix Parliament included is about ensuring that people who were disqualifed just before the law took effect, remained disqualified. And, therefore, it doesn't cover those who were released at that time, and who have later been recalled to prison to continue serving their sentences (a brief explanation: when someone is sentenced to prison, they receive a total sentence, of which they have to serve a minimum amount, before becoming eligible to be released. If they later get in trouble, the Parole board can recall them to prison to continue serving their sentence until it runs out, for people on life sentences, or preventive detention, recall can be made for the rest of their life.)
And it turns out, that, as at April 2013, there were 31 prisoners serving life sentences (and a futher six serving sentences of preventive detention), which were imposed on or before 15 December 2010, but where the recall happened on or after 17 December 2010 (and a further 160 who were back in prison having been recalled for finite sentences). And unless there was some other reason that meant these people were disqualified to vote as at 15 December 2010 (or if they have now been sentenced for a new offence after 16 December 2010), they will all be entitled to vote, even the ones serving life sentences, and even though, if they law had never changed, they would have been banned from voting. The following statement, from a further OIA response I received yesterday, confirms this:
you have also asked whether a prisoner recalled to prison on a sentence imposed prior to 16 December 2010 would be eligible to vote. In these circumstances, a prisoner will be eligble to register to vote provided that they were not otherwise disqualified under the provisions that were applicable before 16 December 2010.
As Prisoner Manager have a duty to provide eligible prisoners the opportunity to vote, I wish them well exercising their voice in the upcoming local body elections! And you lot, too!
Update/Clarification: have changed the wording above to make clear in light of comments in the thread that I cannot be sure that as many prisoners as I describe are certainly within this group who are entitled to vote. The information I received from Corrections didn't list names, and it is possible that the reply ignored separate prison sentences or other disqualifying factors. The OIA requests do however confirm to my satisfaction that there is a category of prisoners - including some lifers - who are entitled to enrol and vote because of the law change banning sentenced prisoners from voting.