- is there a valid expectation of privacy at all in such information;
- if so, is this an unreasonable search?
What does this have to do with DUI in Illinois? 4th amendment issues are regularly tested in DUI arrest situations. You see, almost all DUI arrests involve investigations that are immediate in nature, and happen without any warrant. Getting a warrant slows things down and requires that a judge hear why an investigation needs to go further - the judge determines whether "probable cause" exists to allow a search. This makes on-site investigation difficult, but provides strong protection to rights of the person being investigated. The police would rather not wait, and so, most investigations proceed without warrant. A warrantless search is presumed to violate 4th amendment protection, unless probable cause can be demonstrated.
The practical result is that police typically investigate with an eye towards establishing probable cause (as opposed to investigating with an eye towards exoneration). They'd rather arrest now and ask questions later than slow down and ask careful questions.
Add to this the fact that government is always seeking to expand their ability to "get around" the restrictions of the 4th amendment, and you have your connection between DUI and the Justice Department's desire to track anyone they please by cell-phone without a warrant.
Everything is connected, and the possibility for abuse of power increases every time the power to invade the rights of the individual are pushed further down the chain of command. Let's hope the Courts push back.