It is incumbent upon members of an Garda Síochána to seek to prevent loss of life before it occurs, writes Tom Clonan.
Yesterday's fatal shooting of two post office raiders in Lusk has provoked much debate about the use of force by armed gardaí. The conditions for opening fire or "rules of engagement" for members of an Garda Síochána rest on four central legal principles.
The first of these principles is justification. In order to open fire, a garda must believe that his or her life, or the lives of his or her colleagues or members of the public are at immediate risk.
When confronted by a criminal carrying a firearm - in yesterday's case, a fully loaded semi-automatic handgun - the risk to life is significant. An armed criminal in such circumstances who chooses to ignore a garda challenge to disarm themselves runs the risk of being shot.
This risk exists even if the criminal is not the first to open fire. This prospect rests on the second principle governing the use of armed force - prevention.
In other words, it is incumbent upon members of an Garda Síochána - literally, guardians of the peace - to seek to prevent loss of life before it occurs. Therefore, despite not having opened fire, a criminal who refuses to yield, discard or lower a handgun represents an ongoing and imminent risk to the lives of gardaí and civilians within his vicinity.
The third principle governing the use of armed force is minimum force. It is recommended that gardaí attempt - if possible and practical - to disarm a criminal by unarmed means. In other words, gardaí are expected to physically tackle and overpower armed criminals. Indeed, in the very recent past unarmed uniformed gardaí have managed to physically disarm criminals equipped with shotguns and other weapons.
However, this is not always practical or advisable. In the case of an armed gang, particularly when such criminals are likely to be volatile cocaine users, the use of armed force by gardaí to neutralise the threat to life is perhaps inevitable. In such situations, the guidelines on minimum force advise that it is best to "shoot to wound or otherwise incapacitate". It is never advised in Garda training to "shoot to kill".
In attempting to shoot to wound or otherwise incapacitate a criminal, the challenge posed to armed gardaí is daunting.
Contrary to Hollywood depictions of police marksmen aiming at legs or arms or even shooting weapons out of criminals' hands - it is extremely difficult to hit a moving human target with any degree of accuracy. As a result, police around the world are trained to fire at "the centre of the visible mass" - the torso, chest or abdomen area of the target.
Given the number of vital organs concentrated in this part of the body, such shootings - despite a commitment to minimum force - inevitably result in fatalities. Therefore, yesterday's deaths may not necessarily constitute evidence of excessive or indiscriminate use of force.
The current Garda investigation into the shooting will focus around the final principle governing the use of armed force - "legal requirements". Under legal requirements, gardaí will investigate how many rounds were fired by their colleagues. An inordinately high number of rounds fired would suggest uncontrolled or indiscriminate fire.
In addition, investigators will forensically examine Garda weapons to establish whether or not they were fired in single-shot or automatic mode. Automatic fire is considered inconsistent with minimum force.
The Heckler and Koch MP5 submachine gun carried by certain Garda units - among those units deployed to Lusk yesterday - is capable of being adjusted to fire in single-shot or automatic mode. While the Garda have not yet confirmed which weapon was fired, they did confirm gardaí were carrying Sig Sauer automatic pistols and MP5 submachine guns.
The Garda investigation will therefore focus on the number of rounds fired by individual gardaí, a forensic examination of Garda weapons used and an exhaustive interrogation of the split-second decisions of front-line gardaí based on the principles of justification and prevention.
Dr Tom Clonan is a retired army officer. He currently lectures in the School of Media, DIT.