It’s at this time of year, when the sun is shining (well, it IS at the very moment these words are being written), that carrying out an intensive cell site survey seems almost like a perk of the job. But, as everyone involved knows, a cell site expert shouldn’t expect that each assignment should come with such luxuries. Surveys aren’t always necessary – and even where they are, there could be a smarter solution. In this month’s cell site ‘blog’, Matthew Tart looks at the possibility of using data from previous cases.
This month’s topic: Use of historic cell site data
Q: First of all, precisely what do we mean by historic cell site data?
A: Simply, it’s data CCL-Forensics has generated from carrying out previous cases, which we have organised and stored in an ever-growing database. The reason we have this, is because we don’t carry out static surveys as we have found they have limited repeatability and failed validation (this is described in our previous blog here), which I’ll go into in a little more detail later. So if we’re interested in where a particular cell serves, there is a potential that we’ve already surveyed relevant areas. We’re not (quite!) up to UK wide coverage yet, but the database is growing rapidly, plus we’re getting additional cell data every time we travel between our offices and the general area of the survey.
Q: So, how does this actually benefit the case. Surely, all cases are different, and you may still have to do some surveying?
A: This is not necessarily a replacement for any future survey, it is an enhancement, but it does have some significant advantages. The first being that it can help us to scope out a case, and therefore produce a more accurate strategy – keeping costs down. The more CCL-Forensics know about the network infrastructure of the location in question, the more easily we can produce the most cost-effective forensic solution to the problem at hand. It’s also been useful in court, where very specific questions have been raised about the coverage of a cell; if we have relevant data, our expert in the witness box can easily (and with no cost to anyone involved), use that area information – adding value to proceedings. In short, it means that we simply have more data with which to work – and scientifically, that’s a very good place to be.
Q: But isn’t there a risk that the data may be out of date?
A: The timeliness of data is always a consideration in cell site analysis. One of the most common concerns tends to surround how the network may have changed in the (often) months between the incident and the survey. By using data collected in the past, it could be more relevant to the time of the incident. Additionally further surveys can be undertaken to assess whether that there have been changes in the network over a period of time – and not even the networks themselves can give us information as reliable as that.
Q: Why aren’t all cell site analysts doing this?
A: I’m not saying it’s only CCL-Forensics who are doing it, but there are analysts who practice certain surveying techniques where keeping a database would not be appropriate. Earlier, I mentioned the concept of carrying out static surveys. CCL-Forensics have gone through this at length before, but this just goes to reinforce why turning up at a scene, carrying out a few measurements and then leaving again, is not the strongest piece of science in the world.
Using static surveys each job stands alone and in isolation from any other examination.
Q: It must take up a serious amount of storage space
A: CCL-Forensics had to buy a huge new server to hold this data, but it’s already been worth it. We’ve saved so much time by having access to this data, and passed on significant cost savings as a result. It also means that our clients are getting stronger evidence, effectively for free. It’s stronger because we can more accurately assess service areas, and also get an educated idea of network changes, which can inform expectations at the outset of an investigation and same time during it.
For us, it’s definitely an investment in the future and ideally, we’d like to be a position where we have the whole country mapped, but that’s a little way away at the moment!
To finish with an example: There was an urgent pre case management hearing relating to an incident in a city 150 miles from our base. We were asked to provide some analysis of call data records on a Wednesday morning, which were needed by the Thursday evening.
CCL-Forensics checked our database and found extensive surveys in and around the locations of interest, and could make an informed estimate of cell service at those addresses without the disruption, delay and cost of travelling to the area and carrying out a survey. Basically this would not have been possible, given the time constraint, had we not had the historic data.
Of course it is not just the survey time that causes delay, it’s the preparation, travelling, data manipulation, analysis and reporting of that data. But, as we’d already surveyed the area, the client had the report they needed well ahead of the deadline: something which would have been practically impossible otherwise.
To summarise, every case we do makes CCL-Forensics service stronger.
For more information about historical cell site data usage, or any of the other issues highlighted in this month’s blog, please email Matthew Tart at mtart@ccl-forensics.com or call 01789 261200
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