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.

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New Epilog Signature files released

Epilog Signature files allow users to add specific support for new databases they encounter and although they are designed so that Epilog’s users can create their own signatures when the need arises, CCL-Forensics are committed to updating and releasing a sets of signatures, pre-written and ready to use.

In this new release we have had a real focus on smartphones adding support for:
• iOS6
• Android 4.0 (Ice Cream Sandwich)
• Android 4.1 (Jelly Bean)
• Android 3rd Party Applications
• iOS 3rd Party Applications
• Skype

We always welcome suggestions for signatures that you’d like to see added to the signature collection so please get in touch on epilog@ccl-forensics.com

For more information on epilog please visit our website – www.cclgroupltd.com/Buy-Software/

July 2012 cell site blog: The top five (potential!) pitfalls in cell site analysis.

By Nicholas Patrick-Gleed, Cell Site Analyst

This month’s cell site blog takes on a slightly different style.  The team here at CCL-Forensics has been discussing the most common potential pitfalls encountered in the world of cell site evidence, and thought it would be a useful exercise to commit some of them to the blogosphere.  So, rather than focusing on a particular topic, we’ll look at the top five (as we see them) issues which need to be at the forefront when planning and, more importantly, carrying out a cell site investigation.

We’ve touched on some of these in previous blogs, but they form a concise summary of some of the ‘issues’ we have seen experts (almost) experience.

This Month’s Topic: Five things to be wary of in cell site analysis

1. Exhibits without interpretation

When working for the defence, we regularly see prosecution evidence which can best be described as “exhibits without interpretation”.  A good example of this is a series of maps plotted by an intelligence analyst, who has carried out a series of instructions based on some call data records, but presented them without any explanation of what they mean.  This not only causes confusion and delay within the criminal justice system (the defence will, no doubt, ask for the explanation at some point – so it may as well be provided at the outset) but also means that an opportunity could be missed as part of the investigation stage.  Simply ‘blindly’ plotting information on a map is hardly investigative – but we have seen it more than once.  What is the point of an exhibit without context?

From the prosecution’s perspective this is an obvious potential pitfall – as it means that the evidence does not include something which could enhance the prosecution’s case.

There have also been occasions where the defence leaves it until the 11th hour before ‘complaining’ that the person who has produced the exhibit is not an expert – and the judge could rule that the prosecution needs to carry out more expert analysis.

It’s simply not worth chancing these situations.  Moral of the story: produce exhibits which mean something; it makes for a smoother investigation.

2. Who’s who on the call data records?

Cell site is full of idiosyncrasies.  It’s what keeps us experts on our toes.  But there are small variations between networks and circumstances can lead to major confusion.  The best example of this is when you are analysing a call data record, and the person is in contact with someone on the same network.  There are occasions when both parties cell IDs appear on the same CDR – which can immediately confuse things.  Furthermore, and lets use the ‘3’ network as an example here, if an incoming call to the subject phone is unsuccessful, then the cell ID for the person making the call still appears on the CDR.  This is particularly a problem, as the CRD doesn’t differentiate between the A and B phone (in columns) and so this needs to be taken into account.  It’s pretty easy to spot if there’s a day’s worth of cell IDs in London, and one in Edinburgh – but when both parties are geographically close, then vigilance is the watchword.

This is especially the case if the person plotting the calls is not trained in these nuances – as they may easily go unnoticed.

Moral of the story: be thorough.

3. Timely surveys

Networks change and evolve.  Nothing new there, but the sooner the survey is carried out after the incident in question, the better.  It means the results will be more accurate and better reflect what happened.

We previously touched on our use of historic data, which may help to counteract this problem – and this is a benefit of the robust methodology which CCL uses.  But, timeliness is still a big potential pitfall for a number of reasons.

One of the biggest is the evolution of “Everything Everywhere” – or the merger of
T-Mobile and Orange as most people still know it.  This means that “Everything Everywhere” now has many more channels available than each of their competitors – and consolidating cells seems like a sensible thing to do.  If there are two cells covering the same approximate area, it seems only prudent to use just one of them and either deactivate the other, or reallocate it to, say, the new 4G networks, which have been in the news recently.  This clearly impacts on the survey, especially if the cell in question is no longer transmitting.

Moral of the story: Consider the impact of the T-Mobile and Orange merger before surveying.  What are you expecting to see – and what are you expecting NOT to see?

4. Getting the whole picture – not just a small slice

Cell site is all about focusing on a phone’s movements around the time of a crime, right?  Wrong.  Yes, this is often the best place to start, but it can also be vitally important to look at the patterns of usage within the data as a whole, rather than just isolating and concentrating on a small piece of evidence.

There may be no evidence of a phone being in an area of interest at a particular time, but the best advice here it to stop, look around and think.

There may be behaviour patterns, where the time in question shows some deviation from the norm. There may be evidence elsewhere of the use of ‘clean’ and ‘dirty’ phones.  There may be evidence someone ‘casing the joint’ before the crime, which goes against the usual pattern of usage.

One just doesn’t see these when points are blindly plotted on a map.  The solution is to have as much data available as possible at the outset of a cell site assignment (or as much as can be reasonably requested under RIPA).

At the end of the day, it depends on what question you are trying to answer, but the moral of this story is: Don’t just rely on data from the time of the incident.  More complex investigations need more data.

5. Surveying techniques

Quite honestly, this is something of a bugbear of ours, and a topic which we have covered numerous times.  With that in mind, I won’t go into any major detail, but just summarise something which we think all cell site experts should adopt.  (And we’ve had this published in a peer-reviewed journal, so it’s more than just a passing fad!)

Movement is key to getting an accurate overall picture of how a phone interacts with cells.  The concept of ‘dragging’ a cell can be key to determining if a cell provides coverage at a location.  Driving to a location from a number of directions can result in a different cell providing coverage, depending on which direction you arrive from.  This is because the phone has a tendency to “hold onto” a cell, rather than chopping and changing – (to reduce the risk of a dropped call).  Spot samples (i.e. turning up at a location, surveying without moving, and then leaving, is hardly comprehensive).  This is about so much more than simply dotting the i’s and crossing the t’s.

While we’re on the subject, it’s worth touching on tracking frequencies.  Network Operators, typically use two or three 3G frequencies at their cell sites.  When moving geographically, a phone may use a new cell which uses a different frequency than the original one.  This created a potential pitfall when surveying, as the expert needs to be mindful of how many frequencies are available, and ensure the most appropriate survey is therefore carried out.  The moral of this part of the story: remember there is more than one available frequency – and be as thorough as the investigation requires.

I hope you’ve enjoyed our whistle-stop tour through the potential pitfalls of cell site analysis – and as, ever, we’re always keen to hear your thoughts on the matter.  If you would like to discuss any aspect of cell site analysis, please don’t hesitate to drop us a line at cellsite@ccl-forensics.com

Next month

Next month, Dr Iain Brodie analyses comments made by a judge during a recent case, and highlights what the criminal justice system REALLY wants from cell site experts.

Mystery box reveals digital secrets

Arun Prasannan, member of CCL-Forensics’ R&D team. 

Every now and again, an unusual device arrives for analysis at CCL-Forensics, which proves interesting – but above all, significant to an investigation.

Earlier this month, a UK law enforcement agency submitted what can only be described as a ‘black box’.  It was plastic, no bigger than a packet of cigarettes, and from the outside, it had only a slot for a SIM card and a socket for power.

Working closely with the investigating agency, a member of CCL-Forensics’ R&D team carried out an in-depth analysis of what was inside the device, and what data it was capable of storing.

It was initially suspected that it was some kind of tracking device, and when disassembled, it was found to contain a battery, and two separate circuit boards, to one of which was attached a mercury switch which detected movement.  One board contained all the circuitry one would normally expect on a mobile phone, and had everything it needed to connect to a GSM network.  When examined VERY closely, it was labelled (in very small print) with an IMEI number.  From this, we could identify the board, and then research all the available documents about that piece of hardware.

Interestingly, it was a widely used GSM module found in many mobile devices such as GPS trackers, Fax machines and even some phones.

The SIM card was analysed separately, and it was strongly suspected that there was additional data on the board itself.

Our analysts procured a test module, and carried out a comprehensive technical analysis to validate what data it could store.  It was found to have the capacity to store call data (made, received, missed), SMS and contacts – as well as some call timers.  It was also determined that SMS messages could be extracted without changing their status. 

Following this comprehensive research, it was found that the suspect device DID contain a number of phone numbers and call times – which were presented back to the investigator in the case.  This was a level of potentially vital evidence which would have been missed without this very low-level investigation of the device and the data it contained.

It also highlights the talents of CCL-ForensicsR&D department, and the value investigators can derive by not simply opting for a ‘plug and play’ forensic examination.

For more information, please contact us at research@ccl-forensics.com

Cell site analysis and impactive court presentation

The monthly cell site blog is back – and this month, we’ll be looking at what makes for an high impact piece of cell site evidence in court, as well as how going that extra mile at the outset of a cell site investigation can, in the long run, save time, money and bring your case to a speedier, more positive conclusion.

Impactive court presentation

By Dr. Iain Brodie, Cell Site Expert

Let’s consider a real case which CCL-Forensics investigated on behalf of a UK police force.  We’ll change some of the location and crime details for the sake of confidentiality, and to help with legalities.  The story goes like this:  there was an aggravated burglary at a house in a semi-rural location, and following enquiries, a man was arrested.  It was crucial for the prosecution to demonstrate the man was at the scene and not merely in the vicinity.

The prosecution claimed that the man in custody had made a number of phone calls to an accomplice, waiting outside the property, while the crime was in progress.  They obtained the call data records (CDRs) from the phone company which the phone (attributed to the individual) was connected to at the time.

CCL-Forensics cell site experts looked at the calls at the pertinent time, and could see that there were indeed incoming and outgoing calls – as well as a number of texts.  These events on the CDR used three different cell IDs (mobile phone mast sectors), but all took place over the period of a number of minutes.

In order to determine whether the suspect was likely to have been at the scene, surveys were carried out of the entire coverage areas of these three cells.  CCL-Forensics performed a number of drive surveys, looking at areas where the cells in question would initiate a mobile phone call.  Once these drive surveys had been carried out, for each of the three masts, they were uploaded onto our mapping system and the so-called ‘derived service areas’ were plotted.

The result was instantly compelling.  Like a neat Venn diagram, the areas overlapped, with that overlap area covering a comparatively small area.  Well within this area, was the crime scene.  It was, to a certain extent, a ‘textbook’ piece of evidence.  The fact that a number of cells were used at the time could easily be down to the fact that the suspect was moving around the house, and receiving a different dominant signal from different elevations of the property.

The question you may well ask, is why not just carry out a ‘spot sample’ at the crime location?  Surely this would have yielded the same result.  The reason for this was down to the case conference CCL-Forensics held with the investigating officer, where it was felt that a more robust survey was required to pre-empt any possible challenge from the defence.  This turned out to be a very wise move, as in the weeks after the survey was carried out, the defence put forward an alibi location which was only a comparatively short distance from the crime scene.

When this point was plotted on the same map (without the need to go out and re-survey), it does indeed show that one of the cells served (for initiating a call) at this location – but not all three.  The alibi location was therefore rejected, and based on the compelling evidence from cell site analysis, the suspect was found guilty.

The map shows the coverage areas, along with the overlap, which ultimately proved to be the pivotal piece of evidence in court.  When presented to the jury in this way, the impact is immeasurable. 

Image

The remit here was to find an effective balance between doing the bare minimum, and doing too much – incurring unnecessary costs.  Had a simple ‘spot sample’ been carried out in the first instance, it would have been necessary to return to the scene to carry out similar exercises at the alibi location – incurring delay and cost.  As it transpired, this was not necessary, as the measurements had already been taken.  In addition to this, the way the evidence was presented, showing the relevance of the small area where the cells’ service overlapped, proved to be an invaluable method of demonstrating the point to the jury.  Cell site evidence, when not presented in an impactive way, can be confusing in court – and at worst, can overwhelm those sitting on the jury.  This was an elegant, easily understandable piece of evidence – and it worked.

This enhanced service was agreed by collaboration of the cell site expert with the customer force at the initial case conference. This has shown the value of providing expert advice from the start of the analysis.

The power of the evidence more than justified ‘going that extra mile’ – and it ultimately saved the expense of carrying out at least one additional survey.  I hope this goes to show that a tailored investigation, based on the intelligence of the case and the requirements of the investigating officer, can be a much more powerful approach than a ‘one size fits all’ turn-up-and-survey approach.

If you would like more information about cell site analysis and its use in cases of this type, please contact me or any of my colleagues by emailing info@ccl-forensics.com.  As ever, please keep the feedback to these articles coming in.  We do enjoy reading your comments and opinions.

Keep posted as next month we will look at another aspect of cell site that will make or breaks a prosecution.

Double accreditation is a forensic first

We’re absolutely delighted to announce something of a ‘forensic first’.

CCL-Forensics has become the first UK digital forensic lab to be accredited to ISO17025 – not just for one part of the business – but for BOTH its computer and mobile phone labs.

It’s taken a long time to get here – and having this standard, cements our position as the UK’s leading supplier of digital investigation services.  It also means clients can have the maximum confidence in the quality of our services – especially if the case goes to court.

ISO17025 is a recommendation of the Home Office Forensics Science Regulator, Andrew Rennison – and all labs handling digital evidence should have it by 2015.  Put simply, it is one of the biggest steps forward the digital forensic industry has ever seen.  We’re already way ahead of the curve!

We’ve had ISO17025 for our phone lab for while now – and were one of only a small number of providers to do so.  The fact that we’ve now been accredited for our PC lab is huge news.

So what does it mean?  To give it its full title, it’s called “the general requirements for the competence of testing and calibration laboratories”.  That means that we are required to have in place an all-encompassing set of detailed standard operating procedures.  These procedures show that we operate a management system, are technically competent, and generate technically valid results.

It’s been the result of a lot of hard work – not only by our dedicated quality department – but by all members of staff who have worked tirelessly to ensure all the procedures are developed to the highest standard.

If you’d like more information about our quality standards, please email Dave Lattimore, Total Quality Manager at info@ccl-forensics.com.

Hidden digital evidence part 4

Welcome to the final instalment of our short blog series on places you may not have thought to look for digital evidence.

  1. Biometric data

The use of fingerprints, retinal scans and facial recognition is no longer the stuff of science fiction. Its use may not be widespread yet, but it is certainly becoming a reality on a number of advanced devices.

Computers, laptops and mobile devices may be protected from unauthorised use by such biometric technology. If the data can be retrieved, it can help significantly with the attribution of that device – especially useful on mobile phones if cell site analysis is being carried out as part of the case.

It’s an emerging technology, so keep an eye on developments over the coming months and years. More and more evidential opportunities will present themselves.

  1. Near-field communications

This refers to technology such as the Oyster Card on London’s transport system, and credit cards are also being equipped with chips, which when waved near to a reader device can perform the same function as when it is inserted into a chip and pin device.

Such technology is also finding its way into mobile phones – the Google Wallet has been in the news recently (for all the wrong reasons – namely security issues). This is an app that enables users to pay for goods using their mobile phone using a near-field communication device.

Data may be recorded on the phone – including when it was used, where, and for what purpose. This could be a rich vein of potential evidence, and although its use is not widespread at the moment, it’s certainly worth keeping up with developments.

  1. Games consoles

Games consoles such as Xboxes, Playstations and Wiis now have web browsers as standard. They are much more than just a platform for gaming, with many allowing users to stream music over the internet, rent movies and interact with others online.

External hard drives can also be attached to consoles, enabling people to play music and movies from their collections through the console.

Consoles also enable instant messaging to take place, within games and simply via the messaging function in the console itself.

Use of all these features leaves a digital trail on the hard drive, making such devices a rich source of potential evidence.

  1. Throwaway culture

The focus has been on modern emerging technology, particularly smartphones. But it’s sometimes sensible to consider the other end of the scale: antique technology can also provide interesting evidential opportunities.

Many people tend to upgrade their handsets – and laptops and PCs – and put the old ones in a drawer or box. There they languish, gathering dust, until they’re needed for a criminal case.

It’s entirely possible to extract all sorts of evidence from these older devices, some of which can prove as tricky as the higher-end handsets and computers. Just because a phone or other device looks simple and cheap, the data it may contain could be crucial.

Here’s an example: CCL-Forensics used its web cache toolkit on a six-year-old Nokia 6230i handset and recovered 600 pages of web history – not necessarily the result you’d expect from a modest old device.

  1. With the network provider

A vast quantity of valuable evidence can be gathered from mobile phone network providers using cell site analysis. Network providers keep a variety of information about a phone’s use for a period of time – including the cell masts it used to make and receive calls.

This type of analysis can help to build up a picture of where the phone has been used, and can help in attributing different phones to their users – especially where criminals make use of “clean” and “dirty” phones. (Clean phones are those used for “normal”, everyday activities; dirty phones are those used in the course of crime, and are often thrown away afterwards.)

If a mobile phone has been used in crime, don’t discount the possibility that a wealth of evidence could be gathered using cell site analysis.

Here endeth our list of possible locations for digital forensic evidence – although it is, of course, not exhaustive. As technology advances, more and more types of digital evidence will become available for investigators.

CCL-Forensics’ R&D team keeps pace with new technology, developing tools and techniques for extracting this new data. If you have any questions, they’re always happy to chat. Just drop us a line at research@ccl-forensics.com.