The principal weapons deployed with the Garda Emergency Response Unit (ERU) at the siege in Abbeylara were submachine guns, HK33 assault rifles and at least one automatic shotgun. It is understood Mr Carthy was killed by a burst of automatic fire from an assault rifle.
The firearms used by gardai are essentially infantry weapons suited for confrontations with armed groups, such as terrorist or criminal gangs.
However, there exists a variety of "less than lethal" firearms which could have disabled Mr Carthy without threatening his life. These include guns that fire plastic bullets at sufficient velocity to cause serious but only temporarily disabling injuries. The plastic bullets are accurate at the kind of range from which Mr Carthy was shot.
There is also adapted metal ordnance, which can be fired from the kind of guns the gardaI had which would also have the required "less than lethal" effect. At least three varieties of these bullets are on the market. There is considerable discussion among police forces about the use of these types of weapon.
American police forces in particular have considerable experience in sieges with disturbed people who are often much more heavily armed that Mr Carthy. It is known for US law-enforcement snipers to shoot guns out of people's hands in such sieges. However, there was no opportunity for any such action by the gardai at Abbeylara.
It is understood, however, that the Garda Emergency Response Unit has not been trained to deal with sieges such as the one in Abbeylara. The unit is specifically trained to respond to situations where there is a clear threat to Garda lives.
There is concern among senior gardai about armed groups, including at least one Dublin-based group of armed robbers, that can be expected to open fire on gardai.
This particular gang was responsible for the hijacking and robbery of a security company van carrying cash near Dalkey village in Co Dublin in January last year.
The gang members were armed with assault rifles and were ready to shoot at gardai.
All gardai killed on duty since 1970 have died as a result of confronting armed members of the IRA or other republican splinter groups. As this is the primary source of risk to Garda lives, the ERU's training is tailored specifically to deal with this type of threat. The ERU is the group that is primarily tasked with confronting and arresting armed republicans or professional criminals.
The gardai are trained to kill an armed assailant who is posing a threat to either Garda or civilian life, and an injured man can still pose a serious threat. English police have similar training. In the 1980s an English policeman was shot and killed by an unstable gunman who had been shot in the legs.
The Garda has yet to acquire sniping skills. The Army has at least one marksman on service permanently with each of its infantry battalions. There was one such soldier, equipped with an Accuracy International sniper rifle, available with the 3rd Battalion in the Curragh this week, but there was no call to the Defence Forces for support.
The Defence Forces also has the Ranger Wing with a contingent of up to 30 marksmen with sniping skills. The sniper rifle used by the Army is accurate at around 600 metres.
Military sources said yesterday that the procedure in such a siege would be to deploy at least one marksman with a sniper rifle. This soldier or soldiers would be given specific orders to shoot the gunman in the legs or shoulder as soon as a target presented itself.
The Ranger Wing trains for such sieges and would put in place a Central Control system responsible for assessing the potential threat and issuing commands to soldiers armed with a variety of weapons.
The Garda has not called on the Army's specialist Ranger Wing for armed support for at least a decade. However, the ERU now has a strength of around 50 and has acquired more automatic weapons.P}