“The problem with telephone evidence is that it’s very volatile, and you need to act quickly, because if the battery goes flat you could lose information stored in the flash memory,” Stretton said.
According to analysts, the police are also instructed to take the SIMs out of phones upon seizure to ensure suspects can’t call the phone and remotely wipe data or delete incriminating images. The standard operating procedure is evolving, but if any information is stored in a handset it may be used as evidence against you.
Where in the world?
As the recent Apple tracking furore showed, smartphones routinely track their own whereabouts, and indeed report back to the mothership. But information collected by the handset is only one part of the picture – the authorities have several methods of finding where a handset has been.
“Location information is prime, for both the prosecution and the defence. If you can prove that someone was at a particular location that’s very important,” said Ridley. “If a handset has GPS, then the information stored on the device is more accurate than using cell tower information, which has been used for some time. A lot of people will use GPS, and that information also includes a time stamp, so you can say with a high degree of accuracy that at this time he was here.”
Older tracking methods involve triangulating data from the mobile masts that a phone has used for service. Analysing data about which masts were passed allows police to map a route history.
There’s a lot of collateral information on a device that we can use to build up a picture
Investigative company Forensic Mobile Services says it used this information to build a picture of a recent lorry and driver hijack, when a goods vehicle was stolen for its valuable cargo. “Police inquiries identified seven mobile telephones believed to have been associated with this offence and the investigating officers obtained the relevant call data records for each telephone,” the company said. “Mapping the movement of the subject phones by using the cells used, and producing a table listing chronologically all the calls made and received by the phones, helped secure the convictions.”
Given the wealth of information inside a phone, forensics can quickly build a case. “We’ve seen examples of this being used to help in prosecutions,” said Ridley. “An iPhone had been taken over to Spain, and we could see when the phone was switched on at the airport and where they went. You could argue that it was the handset and not the person, but why would you give your shiny new iPhone to someone else to go on holiday with?”
Using the phone’s history files, Ridley was able to build a picture of the suspect’s routine calls and activities that proved he was carrying the phone at the time.
“We can prove what’s called association, so you can look at the activity on the phone around that time, In the Spanish case we could see the phone was being used for calls and messaging while it was in Spain, and the numbers and messages were close friends and relations of that individual,” he said. “There’s a lot of collateral information on a device that we can use to build up a picture.”
The phone can not only locate where you have been but also what you were doing at the time, which is how the police can tell if a motorist was making a call at the time of a crash. “Time and date on the handset itself can be unreliable, because a user can set it to whatever they want,” said Ridley. “Having said that, if you were texting or making calls, because it passes through your mobile network operator, that is time-stamped by the network and their clocks are accurate. Certainly for court purposes, they’re considered true.”
Where old-fashioned dumb phones had limited memory and function, the modern smartphone connects its owner to the internet, and although that brings many more features, it also means handset secrets are much harder to keep. Assuming you were able to wipe any incriminating data from your handset – no mean feat – the phone’s interaction with the servers at various service providers could still hand incriminating data to the authorities.
According to analysts, the tracking cookies dropped onto a handset by Google and other companies during search and browsing sessions routinely highlight sites visited. Even if you have cleared your history, the cookies could be used to build a picture of browsing habits on a handset. “How to build a nail bomb” sites, for example, could provide a lead in anti-terror investigations.