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Cell Phone Tracking Evidence


Cell Phone Tracking Evidence

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by Larry E. Daniel

We live in a world today where individuals’ movements and locations are being recorded in many different ways. These movements and locations are commonly being used as evidence in civil, criminal and domestic litigation. It is of paramount importance that anyone who is involved in litigation that uses cellular location evidence understands the appropriate and inappropriate use of this type of location data. Recent decisions by some courts have made it possible for government agencies to obtain real time tracking information using an individual’s cellular phone or other cellular device without having to show probably cause or obtain a search warrant.

Additionally, the government and courts continue to maintain the position that obtaining historical call detail records for an individual does not require probable cause or a warrant since the person holding the cell phone is voluntarily providing their location data to a third party, namely the cellular service provider. However, obtaining real time geo-location of a cell phone via the emergency 911 (E911) system still requires either a warrant or permission from the cellular carrier.

Cell phone forensics or cellular data analysis is the process of collecting, analyzing and presenting the approximate location of a cell phone or other cellular device based on data obtained from the wireless company or in some rare cases, from the device itself.

There are several types of mobile cell phone tracking data that can be collected and examined:

  • Carrier based location data is collected by obtaining historical call detail records for a particular phone from the cellular carrier along with a listing of the cell tower locations for that carrier. This mobile data is then analyzed for the purpose of generally placing a cell phone in a location on a map.
  • Cellular data in the form of “pings”, which is real time geo-location tracking of a cellular phone or other cellular device by activating the emergency 911 system (E911), which will then use either a network based or handset based method for locating the phone and will provide a location estimate generated via triangulation of the phone handset.
  • Law enforcement may issue a warrant to get real-time call detail activity for a phone. This is the same type of data contained in a historical call detail record but is provided in real time. Cellular data may come from the device itself in the form of GPS location data either from an application running on the phone, a geo-tagged picture or some other data point.

What is important to understand about tracking a cell phone location or other cellular device is that the accuracy of the geo-location is dependent on a number of factors, not the least of which is the ability of the analyst to properly interpret and present the data and the methods used to present the information.

How is Cellular Data Analysis Used?

Mobile data analysis is used quite often in criminal cases to attempt locate a person of interest, either as they go about their criminal enterprises, or in relation to a particular incident or crime.

This type of mobile data analysis is also used in civil litigation involving vehicle accidents, property damage claims and other types of cases where the location of a particular cell phone at a particular time is of interest.

What about Triangulation?

The term triangulation is often misused and applied to the cell phone data analysis of historical call detail records. Call detail records only contain information about a single cell tower that was used when a call was made.  For mobile triangulation to take place, you have to have a minimum of three points or more of reference.

Is There an Accurate Way to Track a Cell Phone Location?

Yes, but it can only be done in real time by using the cellular system or the cellular phone’s GPS unit to track the phone.

There are basically three ways to locate a phone using technology: Handset based GPS, network based triangulation and hybrid location.

By law, cell phones are supposed to contain a GPS chip for the purpose of location the phone in an emergency. However, even today, not every phone has GPS capability.

The most accurate way to locate a phone is by activating the phone’s GPS unit and allowing that to provide the phone’s location back to the wireless company for transmittal to authorities. Handset based GPS location is supposed to be accurate within 50 feet.

The second way to locate a cell phone is by triangulating the phone using network based location services. What this does is calculate the position of the cell phone relative to three or more cell towers and provides that location information back to the wireless company.

The third way to locate a cell phone uses a combination of network based triangulation and local wireless router locations. However, this is not in common use to the best of my knowledge at this time.

When a cell phone user calls 911 on their cell phone, the 911 operator will get a cell tower tracking location, a sector and in some cases a GPS location for the phone.

However, these locations can be off up to several thousand feet from the actual location of the phone. In order to make sure that the GPS location is as accurate as possible, the PSAP (Public Safety Access Point) operator should manually update the location from their terminal.

Is cell tower tracking evidence junk science?

If your definition of junk science is presenting evidence that is supposed to be based on some scientific method or forensically sound practice, then I think it would qualify as such.

Is there a good use for cellular location evidence?

This issue is the overstatement of the accuracy of the phone’s location.

For instance, if the phone is using a cell tower in a particular town where an incident occurred and the person who was in possession of the phone claims to have been in a different town, it is a simple presentation to dispute the person’s claim.

Another good use is for tracking a phone across a distance based on cell tower usage. While the analyst cannot claim a particular road was used, the cellular evidence can certainly illustrate for a jury that the phone did in fact travel from one city to another or some area to another.

In a recent case cell tower evidence was used to show that a phone call was made near the location of the defendant’s home and a subsequent call was located near his place of employment. At issue was whether or not it would be possible for the defendant to travel to another location, commit a burglary and still make it to the location near his work in the time span between the calls. By combining the cell phone locations, time estimates from Google Maps and the location of the burglary, the jury was convinced that the defendant could not have committed the burglary and still made it to the location of his work in rush hour traffic in Washington, DC.

Cell phone forensic evidence can also be used to show that a phone was near a particular area of interest with some reasonable confidence. And with more data points, this kind of analysis can be helpful in showing that even if the analyst cannot determine why the phone picked a particular tower, dozens of uses of the same tower in a short time would lend itself to showing that the phone was using that tower over other towers nearby on a consistent basis.

The other side of cellular evidence is the use of call detail records to show communications via voice, data or text in the context of a timeline. In a recent case involving a tractor trailer truck involved in an accident it was clear from the call detail records that the driver was not using his cell phone near the time of the accident for phone calls or text messages.The issue for the attorneys who brought in an expert in the case was the time stamps on the cell detail records. Initially it appeared at the times for the phone calls were within minutes of the accident. However, once it was determined that the time stamps were dependent on the time zone of the cellular switch used to handle the call, the time was over an hour prior to the accident. In this case, the truck driver was in the Eastern Time zone when the accident occurred, but the switch that processed the calls was in the Central Time zone and some of the calls reflected the time from the switch. Once the time stamps from the call detail records were moved an hour earlier, the issue was resolved. Contact us for more information about mobile phone forensics and how we can assist your investigation.