how can law Enforcement track people using their phones?

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Watching movies i get this question a lot
If a person throws his phone away , how does the police know who is the owner of the phone?

In: 8

Phones don’t just magically give you the ability to call people, it is a service that you pay for. If you toss your phone away, the phone you pay the cell company for service, then someone who finds the phone can ask the cell company who pays the bill. That will lead back to you.

Of course there are temporary prepaid phones which can be bought with cash leaving no paper trail, and these make tracking down the user of the phone much more difficult if not impossible. This is why the police were peeved at Saul selling such phones out of his car in Better Call Saul.

Here’s a simplified explanation of how a cell phone works:

Your phone has a radio antenna inside that it can use to “shout” messages out around it. When you turn your phone on from a cold start, it will immediately “shout” a message in all directions to the effect of, “Is anyone there?”

The world around you is dotted with radio towers that listen for messages like this. They can usually be identified by their [distinct triangular platforms with tall, vertical slats on the edges](https://upload.wikimedia.org/wikipedia/commons/8/85/Cell-Tower.jpg). They can hear your phone shouting up to a dozen or so miles away in optimal conditions. When these towers hear your phone, they shout back, “Hello, I am Tower #####, I belong to XYZ company, I support this list of protocols…”

Your phone contains a tiny little ID card indicating who you pay for phone service and your account number. This is what your SIM card is. If your phone finds a tower it thinks it is compatible with, it will respond to that tower by presenting the information on the SIM card.

The tower phones up home base at the company who owns the tower and runs a few checks. Verifies if you’re a valid customer, whether you’re up to date on payments and are elligible for service, etc. If all the checks pass, the tower says, “ok, if you want to do data stuff, just let me know”. At this point, the signal bars pop up on your phone indicating you have service. The number of bars tell you how good the connection to the chosen tower is.

Where this becomes important to your question is that the towers keep logs of everyone who tries to connect. If you connect to a tower to get service, it’s known that some device with a SIM card connected to your account must be within a relatively small radius of that tower. If there are many towers in range, some fancy math can be done to triangulate a more precise position of the device. The phone company has access to all of this information.

For the police to get it, they have to ask the phone company to cooperate. They usually do.

Most of the time the law enforcement agency isn’t tracking the phone directly. They’re requesting location data from the cell companies. That might be via a subpoena or search warrant, or if it’s real time it’s called exigent circumstance cell tracing. Like, say you are suicidal and we have your number we can ask Verizon or whoever your carrier is to start tracking your phones pings off the closest cell tower. The data accuracy varies wildly depending on what part of the country you are in, but it’s generally pretty useful.

Keep in mind, this is not the same GPS data that your apps are using, like Google maps for example. That information is way more accurate and the companies in control of the data do not part with it all willy nilly.

I am a dispatcher in a rural county in the Midwest and exigent cell tracing has helped me save dozens of lives.

Last year, someone from my village was missed for a few hours. His family called the police to search for him. They tracked this cellphone with the latest cell towers the phone used. Its not nearly as accurate as gps, but they can determine the location roughly depending how many towers are in the region. They found his car pretty quickly. Unfortunately, the hung himself this day…