Medical implications of the TaserBMJ 2010; 340 doi: http://dx.doi.org/10.1136/bmj.c853 (Published 22 February 2010) Cite this as: BMJ 2010;340:c853
- 1Cameron Forensic Medical Sciences, Barts and the London School of Medicine and Dentistry, London EC1M 6BQ
- 2Injury Assessment and Management Team, Biomedical Sciences Department, Defence Science and Technology Laboratory, Salisbury, Wiltshire SP4 0JQ
- 3Firearms and Protective Equipment, Home Office Scientific Development Branch, St Albans, Hertfordshire AL4 9HQ
Several tactical options are available to police officers facing potentially aggressive or violent people or those with acute behavioural disturbance. The less lethal options include restraint, batons, incapacitant sprays, impact rounds, and conducted energy devices such as Tasers. Although none is risk free, Tasers have attracted particular controversy, with Amnesty International identifying more than 300 deaths associated with their use in the United States.1 However, association is not causation, and other factors complicate the interpretation of fatal outcomes.
The dominant conducted energy device used in police forces worldwide is the Taser X26. This device generates five second trains of electrical pulses that are delivered to the body either by two propelled barbs (which embed in clothing or skin and remain connected to the handset by conductive wire) or by direct contact of the handset’s electrodes (drive-stun mode).2 In the United Kingdom, propelled barbs are used by police in 90% of incidents in which such a device is discharged.3 Anecdotal evidence indicates that the threat of discharge alone may be an effective deterrent.3
In drive-stun mode, the principal action of the discharge is to induce pain (designed to gain the subject’s compliance). When the barbs are propelled, greater electrode separation facilitates the induction of involuntary (and painful) contraction of skeletal muscle mediated by stimulation of sensorimotor nerves.2
The medical consequences of these discharges include barb injuries, localised discharge burns, and injury from falls or from the intense muscle contraction.2 Eye and brain injuries from barb penetration have been documented.2 4 Tonic-clonic seizure after discharge of a conducted energy device to the head has been described.5 Pneumothorax after pleural barb penetration has been reported.6 Six fatal head injuries may have resulted from falls induced by these devices.2 Discharge of a conducted energy device does not induce clinically relevant changes in heart rate, blood pressure, or respiratory related parameters in healthy subjects.7
Whether the current from one of these devices can directly affect the heart is controversial. Atrial fibrillation in an apparently previously healthy child has been associated with exposure to discharge.8 Although induction of ventricular fibrillation is considered improbable,2 the safety margin for precipitating ectopic beats may be smaller because of a lower threshold for their initiation by an extrinsic electrical stimulus.9 Limited data in volunteers subjected to barb application of device discharge across the upper right to lower left anterior chest found no evidence for cardiac capture.10 However, no human studies have investigated discharge applied directly over the heart. In a review of outcomes after use of a Taser against 1201 people in the US, two deaths were noted, neither of which was attributed to the device.11 This implies that the risk of induction of ventricular fibrillation, if one exists, is low.
The device is likely to be used on people who are physiologically and emotionally stressed, factors that may predispose to an increased risk in susceptible individuals (for example, those intoxicated with drugs or those who have cardiovascular disease).
The term excited delirium has been used to describe the bizarre behaviour, often related to the use of cocaine, exhibited by many of those who have died after use of a conducted energy device.1 However, excited delirium is not unique to the use of these devices and is associated with deaths after use of other forms of force by the police.12
The medical assessment of people subjected to discharge from a Taser must be guided, in part, by the range of potential outcomes described above. The assessment must include full past and current medical history, medication use, drug and psychiatric history. Electrocardiography may be indicated, particularly where intoxication with drugs, alcohol, or volatile substances exists or where subjects have cardiac disease or dysrhythmias. Pregnant women should be referred for obstetric review.
A history should be sought from police officers present when the device was deployed, so that the examination can be tailored to evaluate injuries at sites of barb penetration or contact with the stun electrodes, and at other sites where injury may have been sustained (such as the head, spine, or eyes). Acute shortness of breath associated with barb penetration of the chest should be evaluated by radiography.
Barbs may be removed by application of firm in-line traction, unless they are embedded in regions at risk of potential serious injury (such as eyes and the skull), in which case specialist intervention should be sought. Further investigation is unlikely to be needed if the subject is stable and has no illness, condition, or injury beyond the superficial lesions caused by the barbs or stun electrodes.
The UK government has established a standing committee of independent clinicians which provides evidence based information to advise ministers on the medical implications of less lethal weapons used by the police and the army. The committee has advised on technologies such as water cannons, impact rounds, and Taser, and their opinion feeds into user training, deployment policy, and post-incident medical management. Unless dealing with technologies that have sensitive national security implications, the committee’s advice is accessible publicly (for example, www.westmercia.police.uk/assets/_files/documents/sep_09/wmp__1252486507_ACPO_Policy_and_Operational_Us.pdf).
The UK Scientific Advisory Committee on the Medical Implications of Less-Lethal Weapons (SACMILL) monitors operational use, medical reports, and media reports for emerging problems. When necessary, the committee will recommend changes to operational use or training to minimise the risk of adverse medical outcomes.
Reports in the medical literature of serious injuries associated with the deployment of Tasers are few, despite several hundred thousand estimated uses of the device.2 Lesser injuries may be under-reported. It is crucial, therefore, that governments and law enforcement organisations, assisted by healthcare professionals, establish mechanisms to improve understanding of the medical consequences surrounding the use of conducted energy devices such as Tasers and other less lethal technologies. The systematic capture of medically relevant data from operational incidents is a vital step in this process.
Cite this as: BMJ 2010;340:c853
All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare that: (1) None has support for the submitted work; (2) GS is an employee of the Home Office Scientific Development Branch whose role is to assess less lethal systems. No authors have had relationships with companies that might have an interest in the submitted work in the previous three years; (3) Their spouses, partners, and children have no financial relationships that may be relevant to the submitted work; and (4) None of the authors has non-financial interests that may be relevant to the submitted work.
Provenance and peer review: Commissioned based on an idea from the author; externally peer reviewed.