The Supreme Court hears arguments Monday about a relatively new law enforcement technique that allows police to tap into giant tech-firm databases to find out who was near the scene of a crime and may have been involved. Essentially the question before the high court is whether that technique is ingenious, Orwellian, or both? And, ultimately, is it constitutional?

The technique is called geofencing, and it allows the government to draw a virtual fence around a geographic area where a crime was committed. After that, the government seeks a warrant, not to search a home or office, but to require a tech company to search its data to identify any of its millions of users who were within the geofence line at the time of the crime.

The geofencing in this case relied on a Google feature called ‘location history.’ Every two minutes, on average, the location feature recorded where you were by using multiple information sources to pinpoint and record the location of every person with an active cell phone. In other words, if you were within the geofence, and your phone was not turned off, Google could tell quite precisely where you were at any moment of the day or night.