Saturday, 16 November 2013

Talk : Licence to Stun, the Physics of Less Lethal Weapons

A recent UoN Public Science lecture featured a fascinating talk by David Wilkinson (IoP Regional Officer). The talk was entitled "Licence to Stun, the Physics of Less Lethal Weapons" and gave an interesting overview of how the UK authorities characterise and compare less-lethal weapons. This is an exercise that is performed for the UK Police forces at the Centre for Applied Science and Technology (CAST), formerly known as the Home Office Scientific Development Branch (HOSDB). The talk forms the basis for this post, together with some extra links and references.

David explained how, historically, Police forces essentially had two choices of weapons : a truncheon...and a gun - which meant that an escalation in response by the Police very quickly became a very lethal matter.

Previously, this was the entry level of force application.
If it didn't work....

.... the next level up is this Glock

Some History
1960s onwards : The troubles in Northern Ireland were one of the driving forces for development of less-lethal, as described in this timeline

1996: The first incapacitant spray (CS gas) was introduced, but this only has a 5m range and very quickly affects people in the surrounding area as well as the intended target.

1999: The Patten Report, an outcome of the Northern Ireland agreement, looked at the issue of non-lethal weapons. Also, the shooting of Harry Stanley, who was reported to be carrying a gun, but was in fact only in possession of a chair leg wrapped in a plastic bag, further highlighted the need for weapons that bridged the gap between a truncheon and a gun.

As a University of Exeter report states:

"By the end of the 1990s duty of care, health and saftety and impending human rights legislation brought the whole issue of taking postive action to ensure a safe working environment and uphold the right to life, into sharp focus."

2003: The Police Complaints Authority report on "Police Use of Firearms" concluded that :

“….the development of less lethal options – including both the application of existing tactical options such as negotiators and police dogs and the development of new technologies – must be addressed with the utmost urgency to ensure that the police response is consistent with the requirements of human rights legislation.”

An existing steering group, formed to look at the use of less-lethal weapons in Northern Ireland, took on a UK-wide focus and led a review of "less lethal" weapons that were available around the world, which were ranked and assessed according to 22 specific measurable requirements.

The Troubles in Northern Ireland were a
big driver in developing less-lethal weapons

The Essence of the Problem
The problem with designing a "less-lethal" weapon is that on the one hand you want it to give a 100% guarantee of quickly stopping a large angry man on drugs who is running at you, and on the other hand you want it to give a 100% guarantee of not ever killing anyone.

This conflict is illustrated in the chart below, which shows how, in the case of guns, the level of force that needs to applied to be sure of stopping someone is also likely, in many cases, to kill.

In contrast, the ideal scenarios would be as shown below, where a level of force can stop 100% of people and yet kill 0% of them. This is something that is very difficult to achieve in practice. Indeed, none of the "less lethal" technologies available today can guarantee to do this.


The Two Main Methods of Stopping People
All forms of Police weapons work in one of two ways :

Pain Compliance (a truncheon falls into this category - it works by causing pain until the target gives up and complies)


Incapacitance (guns, Tasers, CS gas fall into this category - they work by making if physically impossible for the target to continue whatever they are doing)

David pointed out that pain compliance weapons are less effective on those who have had drink or drugs, and also explained that deterrence was a very effective tool in it's own right, with a large majority of targets giving up as soon as they saw the Taser laser lights on themselves.

The Tasers laser sight was enough to stop the palm tree
dropping coconuts on passers by

The Selection Process
The Steering Group looked at technologies from around the world in their initial screening exercise. Many of these came from the US, not least because there are many thousands of independant law enforcement agencies there to provide a large and diverse market for law enforcement equipment suppliers. In contrast, the 43 Police Forces in England and Wales only use equipment that has been approved by the Home Office.

The evaluation process quickly revealed that many of the technologies on offer did not come up the mark.

Notable examples were the projectile nets, which David described with the comment:
"First you have an angry man with a knife, then after you fire the weapon you have an angry man with a a net"
David also mentioned that there had been talk of electrifying the net but this still left the idea as one that was, in his words "bad, bad, bad".

And then there was the foamgun, which had the twin characteristics of spraying hot sticky foam onto bare skin and also offering the possibility of causing death by suffocation !

Water cannon was another possibility. However, it was pointed out that, on the continent, water cannon works because rioting happens in large open squares in the daytime, where water cannon has the space to be effective. In contrast, the British tradition is to riot at night in side streets - where water cannon vehicles find in much harder to move around.

In a comment that had ones heart swelling with pride, David said that the British were "world leaders in rioting" and also "world leaders in policing riots" - giving the example of how the Police in the UK are able to deal with mobs throwing petrol bombs whereas throwing a petrol bomb in the US will get you shot.

How the Germans do riot control

How the British to riot control

A number of incapacitant sprays were mentioned, including CS gas, Pepper Spray, PAVA, MACE and CR gas.

And there was also a roundup of kinetic energy devices, such as bean bag rounds (which can spin and act a bit like a circular saw), sock rounds, rubber bullets (rather dangerous), plastic bullets (less dangerous) and the current Attenuated Energy Projectile (AEP) (less dangerous still). The AEP is designed to deform if it hits bone, so preventing bone breakages.

The talk described the technology and testing of Tasers in some detail. One surprising fact was that "Taser" stands for "Thomas A Swift's Electric Rifle", which is based on a title of a childrens book that Jack Cover, inventor of the Taser, read as a kid.

The source of the name "Taser"

Tasers are incapacitive weapons, in that they disrupt voluntary control of muscles, thus causing incapacitation. They have a range of approximately 10m, although accuracy does reduce at the longer ranges. In particular, the distance between the two darts widens with distance, increasing the chance that one of the barbs will not hit the target. David pointed out that, if this happens, instead of an incapacitated suspect:
" are not going to have anything other than an angry person with a fish-hook sticking out of them".

The reports detailing the Taser evaluation work are available online, examples being (PSDB Further Evaluation of Taser Devices and Supplement to HOSDB Evaluations of Taser Devices)

The reports are rather impressive in the scope and detail of work that they cover, looking at the performance in cold conditions, effect on pacemakers and even what happens if someone who has been sprayed with PAVA or other flammable solvent containing spray is then hit with a high voltage Taser.

Finally, it is worth mentioning that the talk also included a number of juicy anecdotes. But if I told you those, I'd have to shoot you...albeit with a less-lethal weapon....

Image Sources:Truncheon, Glock, Bloody Sunday, Tree, British, German, Book

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