The Supreme Court on Monday unanimously rejected the Obama administration's position that attaching a GPS device to a vehicle was not a search. However, the justices' convoluted opinions failed to provide clear direction on the Fourth Amendment in a high-tech age.

In United States v. Jones, all nine justices agreed that when District of Columbia police attached a tracking device to a drug suspect's Jeep, that constituted a "search" covered by the Fourth Amendment's protections against unreasonable searches and seizures. That ruling was sufficient to overturn the suspect's conviction.

That alone is significant. It establishes a difference between watching or following someone's movements in public, from a distance, and actually physically intruding on the suspect's property. Law enforcement has long had the power to "tail" a suspect as he walks or drives around town, or to sit in a parked car on a street and watch him come and go from a business or residence. That does not constitute a Fourth Amendment search.

Tapping a phone line on private property, though, requires a warrant. And the court previously has ruled that warrantless wiretaps on public phone booths (remember those?) violated a person's "reasonable expectation of privacy."

The Obama administration contended that no search occurred because the suspect had no "reasonable expectation of privacy" in the area of the Jeep accessed by law enforcement agents (its underbody) and because the vehicle was parked on a public road. The court rightly rejected that logic. The car is private property, and police tampered with it. When you park your car on a public street, you have a reasonable expectation that it won't be physically intruded upon — especially by the government.

If law enforcement can attach warrantless tracking devices to cars parked on streets, they could monitor anyone and everyone with little effort — the information would be downloaded to a database and digitally searched. Physical surveillance (the aforementioned "tailing") requires deploying limited resources (manpower, vehicles, time), and thus forces police to pick only high-value targets.

However, the majority in Jones declined to stipulate whether GPS tracking was "unreasonable" or if it required a warrant. In a concurring opinion, a four-member minority suggested that prolonged technological surveillance in certain criminal cases requires a court's assent, but didn't say whether shorter periods did. We're perplexed as to why our Fourth Amendment rights should depend on the length of surveillance or nature of the criminal investigation.

Jones narrowly affirms that Americans have constitutional protections against certain government searches. But the rapidly changing world of technology presents numerous challenges to Fourth Amendment doctrine. There are, and will be, ways to monitor individuals (and the populace) without physically invading personal property that will alter those definitions, from red-light cameras to unmanned aerial drones.

Furthermore, the widespread, voluntary disclosure of personal data to third parties — via websites, cellphone apps, etc. — weakens the reasonable expectation of privacy. More jurisprudence is needed to draw the lines that protect our freedoms.

REPRINTED FROM THE PANAMA CITY (FL) NEWS HERALD