Since the trackers were introduced in November last year following a Courier-Mail campaign, 20 offenders monitored under the Dangerous Prisoners (Sexual Offenders) Act have been hauled back to the Supreme Court for breaches.

The breaches included substance abuse (38 per cent), supervision non-compliance (33 per cent), possession of pornography (19 per cent) and proximity to victims (10 per cent).

"We're finding out things about these individuals that we never knew before we had this capacity," Mark Rallings, executive director of specialist operations, said.

"I have no doubt whatsoever without GPS and without case management the reoffending rates would be much higher than they are." Read more here.