What Is Cell Site Analysis?

Cell site analysis is a vital part of Digital Forensics & eDiscovery

Statistics estimate that around 94% of UK citizens own a mobile phone. Think about that for a moment. It means nearly everyone in the country is carrying around a device which can provide evidence of where they were at a certain time and even who they were with.

Cell site analysis is the process of extracting such valuable information. The importance of this type of data in criminal and civil litigation is rapidly increasing. In April 2019, it was reported that mobile phones belonging to Steven Donaldson, his alleged killer Steven Dickie and the partner of co-accused Callum Davidson, were tracked moving around the outskirts of Kirriemuir, Scotland, in the hours before the 27-year-old’s body was discovered. A third co-accused, Tasmin Glass’s phone was also operating in the same mast area on the night the murder took place.

Prosecutors allege that Glass, Dickie, and Davidson arranged to meet Mr Donaldson at the Peter Pan play park in Kirriemuir. They then supposedly assaulted him, before taking the victim to the nearby Loch of Kinnordy nature reserve, hitting him with other instruments and setting fire to him and his car.

Being able to (or not able to, as the case may be) place the victim and the accused in the same vicinity at the same time is a crucial piece of evidence, of the type that can be more reliable than witness identification.

So, what is cell site analysis and how does it work?

How cell site analysis works

Cell site analysis looks at the location of a mobile device at the time a call was made or message sent.

In any given area, mobile phone coverage is provided by several overlapping areas known as cells.  These cells radiate in a 120-degree arc from the cell site mast.  This can differ, as some cells have omnidirectional antennas, a class of antennas which radiates radio wave power uniformly in all directions in one plane, with the radiated power lessening with elevation angle above or below the plane, falling to zero on the antenna’s axis.

Mobile phones operating on a 2G network will access several different cells as the phone moves location, constantly in motion to obtain the optimal signal.

To monitor radio signals in the area of certain masts, information from Call Data Records (CDR), obtained from cell phone providers, is used in conjunction with handsets with specially modified software.  Using the CDR and the survey results from the handsets, a range of locations from which a mobile call or message was made can be identified.

Geographical areas relating to mobile phone coverage can span many miles, especially in the countryside.  However, cell site analysis can prove that a mobile phone could not be located within a certain area.

The controversy surrounding cell site analytics

In 2018, the US Supreme Court delivered a landmark decision in Carpenter v. United States, No. 16-402, 585 U.S. ____ (2018). The Court held that the Fourth Amendment protects location records generated by mobile phones.

The case resulted from the US government obtaining six months’ worth of location records concerning Timothy Carpenter, without a warrant.

The Fourth Amendment guarantees the “right of the people to be secure in their persons, houses, papers, and effects against unreasonable searches and seizures.” The question was, did this 228-year-old right extend to mobile phones and other types of modern data?

By a majority of 5-4, the Supreme Court held it did, stating the government must obtain a warrant to access such information.

Chief Justice Roberts, who drafted the majority opinion stated that technology:

“has afforded law enforcement a powerful new tool to carry out its important responsibilities. At the same time, this tool risks Government encroachment of the sort the Framers [of the US Constitution], after consulting the lessons of history, drafted the Fourth Amendment to prevent.”

The UK legal position on cell site analysis

In the UK, data protection is governed by the General Data Protection Regulations and Data Protection Act (DPA) 2018. Using data for criminal investigation purposes is outside the GDPR. Therefore reference must be made to the DPA 2018. Part 3, Chapter 2 of the Data Protection Act 2018 sets out six principles that law enforcement agencies must follow

1. The processing must be lawful and fair;
2. The processing must be specified, explicit and legitimate;
3. The personal data accessed must be adequate, relevant, and not excessive;
4. The personal data accessed must be accurate and kept up to date;
5. The personal data must be kept for no longer than is necessary;
6. The personal data must be processed securely.

Cell site analysis processing must fall within these six principles to be lawful.  One way to ensure this is to use a professional digital forensics provider to undertake the activity.

Lineal has the expertise and tools required to undertake cell site analysis.  If you have any questions, please contact our team on +44 (0)20 7940 4799 or email info@lineal.com.