Cell site blog: ‘consistent’ data, or data ‘not inconsistent’

By Dr Iain Brodie, Senior Cell Site Expert

As cell site experts we are often asked to consider whether cell site data is ‘consistent’ with a specific scenario, in the knowledge that our words can have a significant impact on how a jury thinks.

For example, a typical question put to us might be:  is the data for a particular mobile phone ‘consistent’ with it having been at the scene of a particular incident which occurred, say, in the centre of Birmingham at 12:00 on a particular day?

If the cell site data for the phone shows that it connected via a cell site in the centre of Birmingham which serves the scene at 12:00, then in my opinion it is clear that the data is consistent with the phone having been at the scene. This does not mean that I think the phone necessarily WAS at the scene, as the cell ID used will cover an extended area and, of course, locations that are not the scene. Given the unpredictable ways in which phones are used, however – what data there is supports the contention that the phone was at the scene.

The situation is equally clear cut if, at 12:00, the phone connected via a cell in central London. It is physically impossible for the phone to have connected to a cell in London whilst located in Birmingham, so (if the records from the network are correct) such data would be in conflict with or inconsistent with the phone having been in central Birmingham at 12:00.

If, at 12:00 and 12:01 say, the phone connected via cells in central Coventry, the scenario is slightly different. It is not, under all circumstances, physically impossible for the phone to have connected to a cell in Coventry whilst located in Birmingham. But in all normal circumstances – given the huge number of other more likely cells in Birmingham for the phone to have used, I would still say that this data was in conflict with the phone having been in central Birmingham at 12:00. Such an opinion could be reinforced by carrying out further work if required, but in general such further work would not be required.

But imagine the data was less clear cut. For example, now my phone’s call data records show a cell site in Coventry connected to by the phone at 11:00, a cell site in Solihull at 11:30, a cell site in eastern Birmingham at 11:45 and a cell site in Wolverhampton connected to at 12:30.

In my opinion this data is again ‘consistent’ with the phone having been at the central Birmingham scene at 12:00, as the logical journey of the phone would have been close to the scene. Indeed there are not many plausible routes other than the phone passing close to the scene at 12:00 that could generate such data – although again, I do not believe the data means that the phone definitely was at the scene (and nowhere else) at 12:00.

If, however, the call data for the cell in Wolverhampton was not so. All we would have was call data consistent with movement of a phone towards the centre of Birmingham, but even less evidence that the phone was in the centre of Birmingham. Such a scenario presents quite a grey area for evidence of opinion. Some experts may say the data is still consistent with the phone being in the centre of Birmingham at 12:00, whilst it may be argued that there is, in fact, NO data consistent with the phone being in the centre of Birmingham at 12:00.

I would say that the data is consistent with the phone having travelled towards the centre of Birmingham in the times leading up to 12:00, although there is no data showing it had been used in central Birmingham.

A final scenario would be where the phone connected to a cell site in Coventry at 11:00 and again to the same cell site in Coventry at 12:45. In this scenario it is quite POSSIBLE that the phone had time to travel to the centre of Birmingham and back, but there is no data that would lead me to expect that this had been the case. Here I would use the phrase ‘the data is ‘not inconsistent’ with the phone having been in the centre of Birmingham at 12:00 but there was no data indicating it had done so’.

This may seem like semantics. However, in a case where I gave evidence for the defence earlier this year (in Birmingham Crown Court as it happens), the prosecution expert asserted that there was cell site evidence ‘consistent’ with the defendant’s phone having been travelling away from a location of a crime at a particular time, when the cell site used for all of the relevant calls provided service at his home address. The prosecution expert’s use of the word ‘consistent’ here was challenged and the challenge was accepted by the court.

The judge, Justice John Royce in summing up said:

‘although the data is not in conflict with such a theory <that the defendant was at the relevant scene>.  The data <for the time in question.> is not consistent with being at the site.  It could possibly be that the phone was en route however from the site to the defendant’s home…’

the prosecution has been driven to trying to construct theories because of the absence of solid evidence.  They have tried to make bricks with but a few straws, and have done so with admirable skill and ingenuity.  But is this sufficient evidence to be left to the jury?  Could a jury, on this evidence, properly directed, safely convict?  The conclusion to which I am driven is that they could not. Accordingly, I shall direct the jury to return not guilty verdicts’

Had the prosecution expert’s semantics not been challenged, the outcome may have been different resulting, possibly, in a miscarriage of justice.


Making CCTV evidence compelling in court


Ian Rogers

Ian Rogers

Ian Rogers, a CCTV analysis expert, has 16 years’ experience dealing with video evidence, including ten years with the British Transport Police. In this Q&A blog, he shares his thoughts and observations on how best to engage the jury while presenting robust and compelling evidence. Please feel free to contact Ian with your thoughts at info@ccl-forensics.com.

Q: Quite simply, to begin with: what makes a good court presentation?

A: Where CCTV evidence is concerned, the old cliché of “a picture paints a thousand words” has never been more true. The footage you show, and the way you show it, has to be “impactive” and look professional.

The first hurdle to overcome is to manage the jury’s expectations of what they’re going to see. Far too often, thanks to films and TV programmes, people expect to see something of a better quality than even the most professional expert can produce. I call it the “CSI factor”, as popular crime dramas tend to overplay the type of evidence that can be produced. Generally, even with the sort of advanced enhancement we can carry out, the images tend to be of a much poorer quality than many jury members expect.

The “CSI factor” also raises the jury’s expectation of the technology and equipment which will be used to display the evidence. If you are an OIC (officer in charge) presenting some really pivotal CCTV evidence, first ensure that the equipment does it justice. An old, slightly fuzzy TV is not the way to present a high-impact visual presentation. My top tip here is to make sure you know, well in advance, what will be available in court on the day, to allow you to show your footage. If you’re not happy, this will give you sufficient time to source alternative, more appropriate, equipment.

Q: So, once you’ve got the technology sorted – what about the content of the presentation itself? What makes a professional presentation?

A: One of the first points is to ensure that the work is carried out by someone technically proficient to do so. Secondly it’s imperative that professional, industry standard hardware and software is used to produce the presentation. Always resist cutting corners by giving footage to “that bloke down the corridor” who’s done a bit of home video editing, and has some basic software on his PC. The risk is that it’ll not only look unprofessional, but that the quality of the footage could be degraded and its evidential integrity compromised, particularly if they’re not conversant with the various file and compression formats.

On top of this, the jury may well be able to distinguish between a home-spun presentation and a professional version produced using broadcast-quality equipment. You need to maintain your credibility in front of the jury – and one lacklustre CCTV presentation could go some way to compromising that. Given the pressurised nature of the court environment, a professional DVD presentation with chapters and menus (where there are multiple pieces of footage) not only looks better to the jury, but also reduces the need for the OIC to fumble around finding the relevant piece of content. Credibility is maintained, and the jury have their expectations met.

Q: What about the actual content of the presentation? If you’ve got lots of relevant clips, how do you best plan what you’re going to show and how you’re going to show it?

A: This is where working with your CCTV expert is crucial. Liaise closely with your CCTV analyst to ensure that you have identified the most important parts of the raw footage, and produce an edit list if necessary. Look at how any appropriate enhancement techniques can be employed to improve its clarity. Discuss whether still images can be produced, which emphasise elements of the case, and whether highlighting or annotating the footage would make things clearer and more impactive.

Also, ensure that the menu structure and chapter points (where relevant) are created with you in mind, so you can easily find any part of the footage again if you need to.

Generally, the way to focus a jury’s attention on what is relevant is to use short, well-edited sequences with highlighting, slow-motion, enlargement and enhancement where most applicable. Don’t overuse these features – it only serves as a distraction.

When you’re actually presenting this, think of it as a visual storyboard; and the better you know the content, the more seamlessly you can weave it into the evidence you give in the dock. It goes without saying that practising the presentation will make it natural and intuitive – it’s very often the case that an unrehearsed presentation stands out a mile.

Q: When enhancement has been carried out, and you’re showing something that has been improved from the original, what is the best way of conveying this to the jury?

A: Simply, show them both versions wherever possible, but also explain why the enhancement has been carried out. It’s useful for the OIC to have a broad understanding of what enhancement has been done – just in case of any questions, but enhancement (if done by an experienced professional) is generally accepted in court as admissible evidence. It’s important here to also show if necessary that there is an effective audit trail as to what has been done, by whom and how.

I’m always happy to talk CCTV with anyone with a mutual interest, so please feel free to contact me at info@ccl-forensics.com or on 01789 261200.

Ian Rogers

CCTV Analysis Expert