The Police Ombudsman has said the first use of a Taser by police in Northern Ireland was "justified and proportionate".
The weapon, which uses electricity to incapacitate subjects, was discharged in Derry/Londonderry in the early hours of 16 August 2008.
The incident happened after police responded to a call claiming that a man had locked himself in a house with his two young children and was threatening to kill them and himself. After being struck with the Taser, the man was arrested and the children returned to their mother.
The Police Ombudsman, Mr Al Hutchinson, praised an "effective and successful policing operation", and said the use of the Taser had been the best means of resolving the situation.
"The use of a Taser represented a less lethal option compared to the potential use of live fire or impact [baton] rounds at close range. Unlike handheld batons, it allowed officers to maintain a safe distance from a suspect they believed was armed with a knife," he said.
However Mr Hutchinson has also made a number of procedural recommendations to the PSNI , including that advice to medical professionals on the removal of the small barbs which are discharged by Tasers should be re-circulated.
Police were first called to the incident at about 3am. A woman in a distressed state said that her partner had locked himself in their home with their two children, aged four and five, and was threatening to kill the children and himself. She said her partner had been drinking and had a knife.
Repeated unsuccessful attempts were made by police to contact the man by mobile phone. However, shortly after 6.30am he went to the back door of the property. Officers stationed there instructed him to move into the back yard and clear of the house. The man took one step forward but didn't move further. He was then struck by the Taser discharge and fell to the ground, suffering injuries to his head and elbow, before officers moved in to restrain and handcuff him.
The officer who discharged the Taser later told Police Ombudsman investigators that he believed the children would have been at risk if the man had re-entered the house. The officer said the man had been drinking, was in an emotional and agitated state, was believed to have a knife and had threatened harm to the children.
In line with agreed protocols, the Police Ombudsman's Office was informed of the discharge and a team of investigators was sent to the scene. Investigators carried out house-to-house enquiries in the area and had both the scene of the discharge and the Taser itself forensically examined.
A large number of statements were taken from police officers and members of the public and these were found to be broadly in agreement about the circumstances of the discharge.
Among the other recommendations Mr Hutchinson made for improved police procedures was the suggestion that regional teams of negotiators should be established across Northern Ireland to allow for a quicker response to spontaneous incidents. In this case the negotiators took several hours to arrive at the scene.
The man who was targeted with the Taser later appeared in court in connection with the incident. He was acquitted of all charges against him.