Two suicidal men who were Tasered by police have said they have no complaint about the officers' actions. Both men had self-harmed and refused to let officers administer first aid so a decision was taken to use Taser.
Officers were also forced to use Taser on a suicidal woman at the Mater Hospital in Belfast and on a man who threatened to stab police.
Following investigations into the four incidents, all of which involved knives, Police Ombudsman Michael Maguire said that officers were justified in using Taser.
Inquiries also established that the officers who had used Taser during each of the incidents were properly trained and had been authorised to use the weapon.
"These were potentially extremely dangerous situations for all involved," Dr Maguire said. "In the circumstances, the use of Taser was the least lethal option available to officers, whose actions helped to minimise the level of harm caused."
In the most recent incident, police responded to a 999 call from a man in Randalstown who claimed he had been robbed and was about to kill the robber. He also threatened to kill the first police officer who called with him.
When officers arrived at his home he ignored orders to drop a knife. Taser was used when he approached officers aggressively with the weapon in his hand.
On October 8 last year, police were called to A&E at the Mater Hospital where a woman had a knife and was threatening to harm herself.
Armed response officers spent half an hour trying to convince the woman to drop the knife, before using Taser.
Officers were also forced to use Taser while responding to a report that a man was threatening suicide in north Belfast in June last year.
When they arrived at his home the man began to self-harm and refused to stop. An officer discharged Taser so that first aid could be administered to the man. The man later said he had no issues with the way the incident had been dealt with by police.
In a similar incident in February last year, police in south Belfast responded to a report that a man had self-harmed. When they arrived at his home they found the man on the sofa with a bloody knife.
The man refused to drop the knife and police used a Taser when they realised he was injured. He was treated by paramedics at the scene before being taken to hospital.
The man later told Police Ombudsman investigators that he had no complaint to make about police actions.