The SIM also stores the last five numbers dialled, though the handset may store more. Zdziarski found that the iPhone seemed to store every number ever called – hundreds of them. Unique to the SIM is the last location where the phone was used, identified by country, network and Cell ID (which might need to be checked with the network to get a physical location).
SIM forensics is a field all of its own, and there's a lot of apparently trivial data on the SIM which could be pertinent to a specific case.
According to Kevin Mansell, director of Control-F forensic specialists: "Persistent re-offenders … will often end up buying cheap phones like the Nokia 1100 as they know that will either [have to] dispose of them or have them taken from them." But things get really interesting when a smartphone turns up.
Are you the owner of this mobile sir?
Google mobile search stores the most recent search term in a text file, and mobile browsers cache content along with the accompanying URLs and graphics. Nokia handsets have started automatically geo-tagging photographs, so locations and times can also be established with ease, while the iPhone stores a screenshot of every application as it's closed (so it can zoom into it when the user returns).
Even basic handsets can provide data from unlikely sources: the predictive-text dictionary is a fine source of names and places, even if the presence of an unusual name doesn't prove anything it can be hard to explain. These days even the cheapest phone is likely to have a camera, with photographs that can be vital evidence; and even something as apparently innocuous as the last Bluetooth search (which is generally cached) can turn up interesting snippets of information in the right circumstances.
As phones gain more capabilities so the evidence they are collecting adds up, the iPhone stores voice mail messages locally, while applications such as Ultimate Voice Recorder store every incoming and outgoing call in its entirety: useful for reference, but also useful to the law enforcement community.
The most serious problem for law enforcement is the number of devices and platforms being used, the same problem that plagues most of us including the ex-head of Vodafone. Manufacturers have no interest in working with, or against, the forensic community, but as our friendly personal devices keep recording more and more information about what we're doing, it's worth remembering that all that data might not remain in our pockets forever. ®