Here's the quiz: if police attach a GPS device to your car and track you using that device, without having got a warrant to do so, is the Fourth Amendment violated?
And here's the issue: an Oregonian named Juan Pineda-Moreno had such a thing happen to him and was convicted of growing marijuana after police tracked his car to a suspected growing site. Pineda-Moreno appealed, citing the fact that on two occasions DEA agents placed tracking devices on his car while it was in his driveway – which he considered private, not public, property – and therefore breached his Fourth Amendment rights.
The Ninth Circuit Court of Appeals disagreed, ruling that Pineda-Moreno didn't have any signage or barriers around his property to clearly indicate that it was private property, and since "an individual going up to the house to deliver the newspaper or to visit someone would have to go through the driveway to get to the house," why couldn't the DEA? Further, the court ruled that the underside of his car isn't private because "[t]he undercarriage is part of the car's exterior, and as such, is not afforded a reasonable expectation of privacy."