163217
MOBILE PHONE EVIDENCE
Much was made of the mobile telephone evidence at Chris's trial, especially the evidence of Peter Bristowe, Forensic Engineer, who made two statements, one on December 10th 2004, consisting of seven pages and one on the 27th May 2005 consisting of seventeen pages.
He stated that the mobile phone evidence with reference to Fred Moss's mobile phone and Chris Nudds's mobile could place them in and around the same area on November 30th 2004. This evidence appears not to have been challenged by Chris's defence team, presumably they accepted what was being said by Peter Bristowe as fact. However this evidence is open to interpretation, is not conclusive and should have been challenged in court.
Peter Bristowe does go on to say, in his report, that 'they could have been up to 15km (10 miles) apart, as cell site analysis is not an exact science.
The report below, written by Simon Streggles, MBCS, Director of Disclabs Computer Forensics Services, appeared in a copy of 'Converse' prison newspaper, and supports Peter Bristowe's comments that cell site analysis is not an exact science.
...................................................................................................................
MOBILE PHONE CELL SITE ANALYSIS
JUST HOW RELIABLE IS IT?
Mobile phones used today are transceivers which use little power, combining both a transmitter and a receiver. Although most mobile phones are used to provide a telephone service for the public, they are still receivers and transmitters. Because of this, mobile phones behave in the same way that traditional radio equipment does. Mobile phones operate through networks, (which in the UK are run by O2, Vodaphone, Orange and T-Mobile). These networks are GSM, (Global Systems for Mobile communications), and are built around an array of transmitters, receiving stations which cover nearly all of the United Kingdom. Many other countries follow this similar rule; however, they may have different networks, run by different companies. These 'transmit and receive' stations (or beacons), are known as cell sites. Each cell site consists of multiple receivers and transmitters and of course the relevent aerials associated with each one. These sites are often on masts, can often be sited above police stations, schools and other tall buildings (giving clearer transmissions therefore clearer line of site transmissions).
Each cell site as a reference number and name. Using this information, one can state exactly the area of the cell site. From this we can pinpoint to a very small area if the suspect phone has been used in this area. Whenever a mobile phone is 'on' it scans the radio frequencies assigned to it by its designated network provider, and then links up with the cell that gives it the best coverage. This process is called registration, and is of course necessary for the networks so that they can direct incoming and outgoing calls to the correct phones.