While the positive yield of nabbing criminals in the act will no doubt provide a valid argument for the use of global positioning systems as a preventative measure to criminal offenses, the bottom line is that even those who have previously committed crimes are subject to the same protections under the constitution as those who have not. The placing of a GPS device on the basis of suspicion is akin to a breach of property and privacy. If officers believe they have probable cause to breach property, then they also have sufficient reason to seek a warrant and take that extra legal step.
While we find it hard to argue with the idea of "better safe than sorry," the crux of the issue is that once a legal precedent is set on the use of tracking devices without a warrant, then the majority of us are vulnerable to such an invasion of privacy –whether or not we've done anything to infer probable cause. After all, if a mere blip on our record can be leveraged as such, then we all our going to have to do our best to stay squeaky clean. (more)