Evictions have begun at Dale Farm. In a morning characterised by violence, protesters and residents have set fire to caravans and thrown objects at the police. Perhaps most striking, however, is the fact that two protesters have been Tasered.

Tasers are stun guns, which fire needle-tipped darts up to 6m away to deliver a disabling, 50,000-volt shock. The dart can penetrate clothing up to two inches thick, and leaves the target incapacitated. The Arizona-based manufacturer, Taser International, says they are designed to temporarily stun a suspect to facilitate their arrest.

Until 2004, only firearms officers were allowed to use them, but in 2008, they were rolled out to all 43 police forces in England and their use increased by a third.

The stun guns have caused considerable controversy in Britain, with Amnesty International maintaining that they should only be used where lives are at risk.

Certainly, they should not be used for crowd control -- as the Association of Chief Police Officer's (ACPO) own guidelines states. Christian Papaleontiou of the Home Office's policing directorate reiterated this to MPs last year. Speaking to the home affairs select committee, he said:

We again support the ACPO guidance, which is very clear that Tasers should not be used in terms of a crowd control measure in public order scenarios.

On top of this, ACPO policy guidance on the use of Tasers, dated December 2008, specifies that Tasers must only be used

Where the authorising officer has reason to suppose that they, in the course of their duty, may have to protect the public, themselves and /or the subject(s) at incidents of violence or threats of violence of such severity that they will need to use force.

It is reasonable to extrapolate from this that Tasers should not be used against protesters. A statement by Essex Police said that officers had received "intelligence which informed the commanders that anyone entering the site was likely to come up against violence and a serious breach of the peace would occur". This suggests that their defence will be that the use of force was justified.

However, according to eyewitness reports, police used Tasers as soon as they entered the site (as seen in the picture above), implying that they began with an unnecessary level of aggression. Moreover, given that protestors' "missiles" were, in the words of the police, made up of "rocks and liquids", it is difficult to see how a 50,000-volt stun gun is a proportionate response.