SatNav Forensics

by PAUL VELLA of Evidence Matters

SATNAV DEVICES HAVE become so commonplace in modern society that I wonder if in a few years when I explain to my young children whether they will believe me when I tell them that we used to drive to places by simply ‘knowing’ how to get there or by reading a map.

Yet, the SatNav hasn’t been around very long. The Global Positioning System (GPS) was established in 1973 by the US Department of Defense and comprises of at least twenty-four satellites (there are currently twenty-nine operational satellites in orbit). These satellites transmit a synchronised time signal, which allows a device on earth to calculate how far away each of the satellites are (based on how long it has taken the signal to reach the device), and can then triangulate its position provided it has received signals from at least three satellites.

Whilst intended as a military project, in 1983 a Soviet interceptor shot down a civilian KAL 007 that had strayed into prohibited airspace due to navigational errors killing all 269 people on board. Following this, US President Ronald Reagan announced that GPS would be made available for civilian used once it was completed.

By December 1993, GPS had achieved initial operational capacity, and in 1996, recognising the growing importance of GPS in civilian use, US President Bill Clinton issued a policy directive establishing GPS as a dual-use system and established an interagency GPS executive board to manage it as a national asset.

It is sometimes hard to believe that the first TomTom device didn’t reach the shelves in Halfords until as late as 2004, although prior to that it was possible to install TomTom software on PocketPCs equipped with a GPS receiver.

In order to receive a signal, the SatNav device must have a clear view of the sky, and I always get a kick when TV shows like 24 somehow manage to ‘track’ people in the subway or multi-storey car parks using GPS.

So, history lesson over, what can we learn from a SatNav? Quite a lot actually. Depending on the make and model, different devices retain different quality and quantity of data. A device I examined recently had maintained a log of the past 240 planned journeys, in addition to the last few ‘recorded’ locations where a ‘GPS fix’ had been obtained and stored. One of these in particular showed the defendant going to the wrong address and then plotting a new route to the correct address just half a mile away.

Some devices will record dates and times of journeys, others won’t. Likewise, some devices will maintain ‘track logs’ whereas some others won’t.

Some SatNav devices will connect to a mobile phone via Bluetooth, and can maintain a copy of incoming text messages as well as logs of calls made and received by the mobile phone whilst in the car.

Of course, it isn’t just TomTom devices that are of interest, one case we were instructed on involved smuggling drugs across the English Channel. The handheld GPS receivers had previously been examined by another firm of experts, but they had failed to extract track logs which enabled us to provide details of the previous two dozen or so journeys across the channel by boat, including the dates and times of departure and arrival.

When we started conducting forensic examinations of SatNav devices most of the data had to be decoded manually, but today there are many tools at our disposal to help us interpret the data which helps tremendously in providing a fast turnaround and keeping the costs down.

Of course, the true purpose of a SatNav is to ensure that us men never have to admit defeat and ask someone for directions, which perhaps is the real reason they are so popular.