Tag: A Level Computer Science

Why GPS Isn’t The Solution To Knife Crime – A Computer Science Approach

This morning I was sent a link to a tweet suggesting that I read the responses for some amusement. I duly did so, and I’ll admit some of the responses did make me chuckle. But then I considered the suggestion from a teacher’s perspective and realised that the suggestion really did come from a place of good intention, but also from an ignorance of technology.

Tweets like this one by @td_ward highlighted the reason for me writing this rather lengthy blog. The frustration expressed by people who understand technology is utterly understandable, but are we doing enough to educate those that don’t understand?

In 2017, 0.4% of female A Level students, and only 5% male A Level Students elected to study Computer Science according to the Department for Education’s report on take-up of academic subjects in 2017. Those numbers have risen slightly, but not enough. The removal of the GCSE IT qualification has reduced the numbers of students studying a computer technology subject substantially.

Why have I included those statistics?

Because, the fewer young people that study technology but use devices that seem to work as if by magic, the more people will make mistakes like Scott Mann. So, rather than ridiculing him, I want to use this as a learning opportunity to look at the potential for technology to make an impact on knife crime, not just in the UK, but anywhere.

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One of the things we teach in Computer Science is to avoid the solution until we understand what problem we are trying to solve. Decomposition of a problem often allows us to identify problems that we didn’t realise we were actually trying to solve.

Much like rubber duck debugging, explaining the problem in enough basic detail so that even a rubber duck could understand quite often helps us to identify the real problem on our own (many thanks to my husband who acts as my own rubber duck when I get frustrated with code on here! Quack quack)

What Problem Are We Solving?

Knife crime is quite a big issue and has so many aspects that a simple solution may well not be enough. So let’s decompose the problem (this is a fictitious conversation to show how I would decompose the problem – please do get in touch if this could be more accurate):

What’s the problem?

We need to solve knife crime

What would a solution look like?

A reduction in the number of cases

Does the problem lie with the weapon or the person?


Which one could technology help with more?

The knives

What is the problem with the current solution? (carrying a knife with a blade longer than 3″ is already an offence)

We can’t trace the knife to the person

Why doesn’t DNA testing work?

It takes too long & isn’t always accurate

What information do you want from finding the knife?

The owner, the address, and for it to be a deterrent


Using this conversation in my head, I would assume that what Scott Mann was actually trying to suggest was a way of firstly deterring people from carrying knives, but also a way of reliably tracing them back once they were found. I could of course be wrong and he was indeed trying to track each one like a vehicle can be.

So let’s look at some possible devices that are small enough and would link to his idea:

An NFC Chip

The chip that I believe Mr Mann was referring to (I could of course be wrong, but I live in hope) is actually an NFC, or Near Field Communication chip.

Using the breakdown of the problem above, this actually could be a potential partial solution. NFC requires no power to run, so could be easily implanted into the handle of a knife, or added as a sticker or such once a knife is bought.

NFC technology is wonderfully useful for storing small amounts of registration data. There are a number of different types of NFC – those that we use in our phone are powered and can send & receive data such as files and contact information, or the less powerful passive NFC used in payment cards that allow a reader to access information using a ‘tap’ of the card.

What’s the downside? Well, using NFC to identify a knife would be as simple as having an app on a phone to read the data, but only at distances of a few centimeters. This would be fine for searches, or in the sad cases where the knife was used. However, the data would be accessible to anyone with a reader so there would be a serious issue of data protection. Inside the home, this would be less of an issue, but in the case of work or fishing what would prevent someone from walking past and reading your data? In short, not a great deal.

It is for this same reason that anti-NFC wallets have been created.

An RFID Chip

RFID, or Radio Frequency Identification was actually developed before NFC and like NFC has a variety of types both powered and unpowered.

If you’ve ever taken your pet to be “microchipped” then you’ve used a form of passive RFID. Your pet is not actually bionic or powering the device, but the chip is powered when a reader is placed nearby and activates the chip to send data.

RFID chips can be placed in an amazing amount of devices and are often used to open doors via security cards, or to save identification information to retrieve a lost device. The potential to use RFID as an identification tool has some distinct possibilities – RFID can be programmed to only be read by certain devices (like pet microchips), although there’s nothing to stop someone developing a reader as this is an open standard and would need to be for all manufacturers to include them.

Passive RFID can also be read from up to 25m which means that the ID could be read from a safe distance (but probably not soon enough). The longer range active RFID can have ranges of 100m, but then how many knives are there within a 100m range at any given time, and the issue of power crops up again.

RFID is indeed small enough to add to any knife, but then a database of every knife would be needed. The owners of the Pet microchip database will tell you how difficult it is when the users don’t update their information – this has become easier with the introduction of a website to keep them up to date. But, if people are reluctant to update ID information about pets that they love, how likely are they to update data about their kitchen implements?

A GPS Chip

In his original tweet, Mr Mann suggested placing a GPS device on every knife sold in the UK. GPS chips can be quite small, but there are a few issues with this.

GPS is a wonderful invention and has been used to track people and devices to within a few meters. I use this on a daily basis with my children as they come home from school (with their consent!), and would be quite literally lost without it every time we travel.

Unfortunately, placing a GPS device requires a power source. Try an experiment with your phone to prove this: Monitor your battery usage for an hour with your location services switched off, now using the same apps & in the same place switch on your location services & monitor your battery usage for another hour. The difference in power consumption will explain the first issue.

In order for this system to work, you would need to charge your knives. Simply allowing the battery to run out would then take the knife “off the grid”.

The second issue with this is detection. I mentioned that I use GPS to track the location of my children (or at least their mobile phones – they don’t have GPS implanted in them!), but with their consent. In order to see their position they have to individually allow me to see their position, and it’s something that they can switch off at any time. An ethical debate comes up when a device like this is embedded in a device with implied consent that the location can be seen by a governing body.

  • Is implied consent enough? (GDPR)
  • What if the knife is stolen?
  • What if you use them for work?
  • Do the benefits outweigh the loss of privacy?
  • Who is monitoring the data?
  • What if the data is hacked?

Of course, in almost every news story my inner teacher will spot an educational element, and this was no different. In fact, in writing this blog, I spy an exam ethics essay question!


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