Cell phone data as investigative tool

The ubiquity of mobile phones has led to all manner of novel uses. The fact that each phone transmits data as to where it is enables others to use it to pinpoint their location at any time. This was one source of data that was used to identify a suspect in the notorious Gilgo murders, even though burner phones were used.

Investigators had gone backward through phone records collected from both midtown Manhattan and the Massapequa Park area – two areas where a “burner phone” used by the alleged killer were detected, according to court documents.

Authorities then narrowed records collected by cell towers to thousands, then down to hundreds, and finally down to a handful of people who could match a suspect.

From there, authorities worked to focus on people who lived in the area of the cell tower who also matched a physical description given by a witness who had seen the suspected killer.

In the narrowed pool, they searched for a connection to a green pickup a witness had seen the suspect driving, the sources said.

Investigators found Heuermann, who matched a witness’s physical description, lived close to the Long Island cell site and worked near the New York City cell sites where other calls were captured.

Kevin Drum describes another less dramatic use and links to a study that uses cell phone data to study weekly church attendance. It turns out that the number they find is far less that what surveys that ask people to self-report attendance get.

I guess that we should not be surprised that in a country where there is such a high level of public piety and where being religious is seen as being essential to being a moral person, people will fib about how faithfully they practice their faith.


  1. Rob Grigjanis says

    It’s not clear to me how they get this data. GPS? What if many churchgoers leave their cellphones at home?

  2. Dunc says

    Rob: I would expect it’s from cellular geolocation, which is done at the network level and not at the handset (and also doesn’t depend on the device having a GPS reciever at all, or any opt-in from the user). Basically they track the timing of the signals between the device and multiple base stations and figure out the location from that (the device is pretty much constantly negotiating with the stations in range to determine which one it should be connected to).

    But yes, this is really a study of how many cellphones attend church, not people. However, I strongly suspect that the number of people who don’t take their cellphones to church is not nearly big enough to account for the discrepencies.

  3. sonofrojblake says

    Marcus Ranum calls this the “retroscope”. Search that on ftb for more.

  4. says

    Regarding getting the data (and I’m not saying this is what the study did), but think, how does Google Maps show you traffic data? Real-time data from the phones of people with a Google app running on it. The other day, when deciding when to go to my local barber, I saw the Google time-of-day usage chart in my search results. Took me a bit to figure out they were doing the same thing there (and could also tell me how long the average person spent there).

    Regarding burner phones, how would they track those phones to him? The whole point to using a burner phone is to use cash to purchase it (if you used a credit card, shame on you). And not to load it with anything that identifies you. I’m suspecting that the suspect took none of those precautions.

  5. says

    Mano, thanks. What the article does not say is how those burner phones were linked to Heuermann. But may there’s a hint: “Incriminating items that police allege to have found included cellphone billing records for Heuermann.” That suggests to me that he was paying those cell bills with a personal credit card. The alternative would have been to buy minutes for the cards using cash.

    OK, looking further (at the indictment itself), it look like what they managed to do was a massive data search and discovered that Heuermann’s acknowledged cell phone was always in the same location as one of the burner phones. That’s some pretty sophisticated work.

  6. anat says

    Does cellular geolocation work when cellular data is turned off on the phone? I have mine off unless I need it to be on (have wifi at home and at work, rarely use the phone in other locations).

  7. DonDueed says

    @anat: Unless your phone is completely turned off, it is continually announcing itself to nearby towers. You can still be tracked by means of the basic telephone function of the device.

  8. sonofrojblake says

    ALL of this has been covered more than once over on stderr. Seriously, do check it out

  9. sonofrojblake says

    I’ve posted four relevant links to stderr postings, but they’re bafflingly “awaiting moderation”…

  10. Holms says

    Four links… in a single post? Three links gets the post moderated. WordPress settings I think.

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