Sorry if I cover points already made, dropping in and out of this.
bob - you asked what misuse I could foresee. I'll answer that in two ways:
1. Misuse doesn't matter. The default point of society, as evidenced in constitutional principles of the rule of law, is that we are individuals to be left to our own devices and not subject to search, seizure, imprisonment, intrusion etc etc by the state without substantial reason. The default position in the "misuse" argument is that the Government has the right to intrude in ways they see fit and it is the citizenry who must prove why they shouldn't.
The one way to argue DNA seizure within the "individual right to privacy and liberty" argument is that the public good is significant enough to outweigh the intrusion on basic liberty. I have sympathy for that view - but, again as evidenced in basic constitutional legal principles, that intrusion has to be for substantial and specific reasons and not left to law enforcement to dictate it - it requires the oversight and authority of an independent judiciary. This Bill does not provide for either a substantial/specific need or independent oversight, basic constitutional requirements when we believe we can override personal liberties.
2. Given that, misuse could take multiple forms
over time.
The most obvious primary one is false arrest in order to get a DNA sample to do a blind fishing trip. This is clearly outside intent of the bill but something the Police would pretty obviously try on.
Broader long-term misuse could take the form of unauthorised DNA scans to determine some element of genetic/medical makeup of an individual.
How about ethnic profiling by private companies? Never happen?
Ummmmm... And that's the ONLY country who runs a similar scheme, which in itself has been judged illegal.
I'm not some super liberterian who sees Big Brother in every CCTV camera, but having spent time in the UK recently where they have completely lost that assumed right to individual privacy and liberty through a creeping state that overrides those rights to liberty constantly and now has a huge National Identity Database and numerous examples of data matching, swapping and selling to private companies.
The starting position is the state doesn't interfere. When you work back from there I can't find that the police having carte-blanche to take DNA from an incredibly broad list of individual people without specific reason is a tenable position. Even with the few extra prosecutions it may engender.