The Police Ombudsman has concluded that police were justified in discharging a total of 42 AEP rounds during serious rioting in Belfast's Broadway area on 11 and 12 July 2010.
During more than four hours of serious disorder, police were attacked with stones, petrol bombs and other missiles. A number of vehicles were also hijacked and driven at police lines before being set on fire.
The violence happened only nine days after previous rioting in the same area - which is at an interface between the largely Nationalist St James/Falls Road districts, and the predominantly Loyalist Village/Donegall Road area. Police discharged a total of 22 AEPs when trouble between rival factions flared on 3 July 2011.
As a result of the previous disorder, police units had been deployed to monitor the area as the Loyalist community prepared to light a large bonfire which had been erected as part of the annual Twelfth of July celebrations.
During the course of these patrols police officers discovered stockpiles of petrol bomb making equipment on the Nationalist side of the interface. This was seized and disposed of.
At around midnight on 11 July, senior police commanders received reports that a Nationalist crowd, which had gathered in the Broadway area on the opposite side of the roundabout from the Loyalist celebrations, was growing in number.
Police then formed a line to prevent any attempt by the crowd to enter the Loyalist area. Police on the ground subsequently reported that they were coming under heavy attack from the Nationalist crowd. Petrol bombs, heavy masonry and other missiles were reported as being thrown at police lines.
Police employed a number of tactics to try to deal with the disorder, including the tactical use of their vehicles, engagement with local community representatives, and use of public address systems to issue warnings urging those involved in illegal activity to disperse.
These warnings went unheeded, and as the violence continued two hijacked vehicles were driven at police lines and set alight. A number of police officers were also reported to have sustained injuries.
At 00:47 hours, the senior commanders overseeing the policing operation authorised the use of water cannon.
This also failed to quell the disorder, and at 01:11hours police commanders considered that there was a serious risk that officers could sustain serious and/or life-threatening injuries. On that basis, they authorised the use of Attenuated Energy Projectiles (AEPs).
Vehicle mounted public address systems were then used to warn the crowd that AEPs would be used if the violence continued. These warnings failed to halt the violence, and between 01:11 hours and 03:03hours police discharged a total of 42 AEPs at identified rioters.
All discharges of police firearms are referred to the Police Ombudsman for independent investigation. During their investigation of the use of AEPs in this incident, Police Ombudsman investigators examined all relevant police documentation, as well as police radio transmissions and CCTV footage of the disorder.
This evidence showed that police commanders kept the authority to use AEPs under continual review during the period of their use.
At 03:03hours when senior officers were informed that the situation had calmed, and that the water cannon was proving effective in maintaining a safe distance between rioters and police lines, authority to use AEPs was rescinded.
It was temporarily reinstated after the water cannon developed a technical fault, but only for the period prior to the arrival of a replacement.
Authority to use AEPs was finally rescinded at 04:05hours when the rioters had largely dispersed and attacks on police had ceased.
Having assessed the evidence, Police Ombudsman Mr Al Hutchinson concluded that the use of AEPs had been "lawful, necessary and proportionate."
"The evidence clearly indicates that the violence posed a serious threat to the safety of police officers and members of the public," he said.
"Police employed a variety of tactics in a bid to quell the violence, but when these failed, and having no other viable options available to them, a decision was taken to deploy and discharge AEPs at identified rioters.
"This decision was lawful and in accordance with existing legislation and necessary given the risks the violence posed to police officers and members of the public."
Mr Hutchinson added that each of the officers who had discharged AEPs had been properly trained and authorised to do so.