Over the last few years, the concept of geofencing has become a mainstay in marketing circles, and more recently it has become useful to law enforcement. It’s powerful technology that can be used for good or evil, depending on which side of law enforcement you’re on. I believe that location data is intruding on our privacy in ways that we don’t entirely understand, and the geofencing debate brings many of the problems into the light.

How does geofencing work?

Essentially, companies or law enforcement draw an imaginary boundary on a digital map and all cell phone location data is collected within that boundary. Then the company can use the location data to sell users something or law enforcement can use the data to question witnesses or make arrests.

The concept of geofencing was originally used to provide businesses a way to target potential customers in a hyper-local way. For example, a store could offer all people within one block a coupon for discounted merchandise. Another example was a car dealership offering people leaving a rival dealer competitive financing (article).

I have personally seen this work in legal marketing. I had a company pitch me on the idea of showing my ads for personal injury work to people visiting the local emergency room. That was a few years ago so that gives you an idea of how long this technology has been around.

The technology works because of two things: (1) everyone has a smartphone and (2) virtually all of us are unwittingly giving our location data to a company (probably Google, but there are others). Given that 95% of American adults have a smartphone, this data collection and use are extensive and its applications are numerous.

In comes law enforcement. Of course, this technology is extremely useful to police. They do the same thing as companies – they create an area and track all cell phone data within the area. That data is provided anonymously to detectives who then create a list of suspects based on cell phone movements. This has been used to solve a variety of cases including home invasions and murders (NY Times article).

On its face, this all sounds good, but let’s break it down and discuss where this technology potentially goes awry.

The Good of Geofencing

Geofencing can help law enforcement solve crimes that could not normally be solved. It helps to locate suspects and witnesses. There have been a number of high-profile cases solved using location data collected by Google. For example, the NY Times article I cited earlier is about solving a murder that, without geofencing, would have likely gone unsolved.

Catching bad guys who wouldn’t have been caught using normal means is great. It helps make the world safer and makes it harder to get away with crime.

The Bad of Geofencing

Many of the stories where geofencing was used to solve a crime involve the questioning and arrest of innocent people. That occurs because geofencing warrants cast a huge net. These warrants can cover multiple blocks of distance and time frames stretching into days or weeks. Potentially hundreds or thousands of people can be included in these sweeping warrants.

Imagine for a second being arrested for a crime you did not commit simply because your cell phone was located near the commission of a crime. Suddenly, it’s on you to provide an alibi or to explain why you aren’t the criminal responsible for the crime. Assuming you have that kind of evidence, you could still end up imprisoned for days or weeks until everything gets sorted out.

You might be thinking that warrants of that scope probably come under tremendous scrutiny from judges. I suspect that you are wrong. When I was a prosecutor, officers would routinely come into court to ask the judge (any judge) to sign warrants. I don’t recall a judge ever refusing to sign a warrant. In fact, I don’t recall a judge ever really asking any questions about the warrants. Usually, the judge just signed them, maybe asking a couple of generic questions of the officer. Not exactly the oversight that we would hope for.

There is the added problem that judges may not understand what geofencing is. We have an aging judiciary who frequently struggles with basic technology, and these warrants are not offered with an expert to explain how thousands of users’ data will be collected as part of a geofencing warrant. In fact, and with no disrespect to law enforcement, officers are disincentivized from offering that kind of information to judges because if they had all of the information, judges may refuse to sign such warrants.

The fact is that this kind of data collection ropes many people into a criminal investigation who would not normally be suspects. That level of contact with law enforcement is not usually good for the average citizen.

The Ugly of Geofencing

This mass collection of data could mean real trouble for protestors and social activists. For example, police could collect data on the entire protestor-controlled region set up in Seattle. Then, using that data, they could determine who was most active in the protests and arrest those people. The mere fact that this technology exists may encourage people to avoid protests for fear of being targeted by law enforcement.

Look, I’m not a doomsayer. I know that what I just wrote is a stretch. However, the technology could absolutely be used to police otherwise lawful actions. It’s extremely important that we put limitations on police use of technology before it gets out of hand.


Geofencing is an incredibly powerful tool. It can be used by law enforcement to solve previously unsolved crimes. But if unchecked, the technology could easily be used to oppress freedoms and incarcerate people needlessly.