This is not a "balance" of rights, it's a line over which the government should not cross. It's a line of which the National Party are utterly unaware. Involuntarily taking and keeping the DNA of arrested people crosses that line. According to National's website, their proposed policy goes like this:
Take DNA from all convicted criminals.As you see, the headline is contradicted somewhat by the small print. You might also note that the policy is supported by the ACT Party, who went into the last election declaring "DNA is the modern fingerprint and should be used in the same way, eg. on arrest if police deem appropriate." These people have no conception of legal restraint. (As MikeE says, another reason to hate the Tories.)
DNA testing can make a huge contribution to solving crime by helping police target criminals committing most of the crime. At present, we add to the DNA database only samples from those convicted of offences generally attracting sentences of more than seven years. Under National, every person arrested will be DNA tested. If they are convicted, their DNA will be added to the database. If they are not charged or are acquitted, the sample will be destroyed. [Emphasis added.]
'Not PC' says by all means take the DNA of people who have committed crimes against the individual rights of others and been convicted for it, but by no means should the police be given power to take it and keep it from those who have simply been held or arrested -- not unless they have volunteered permission. That is stepping over the line from protector to abuser -- it is the very reason good law respects the presumption of innocence.
The National Party has had the presumption of innocence doctrine in its sights for some time. Such a long-held cornerstone of liberty against state power should not be overturned so easily, or at all.