An aggressive Daniel John Morrison, 21, struck the policeman twice to the face with his left fist, the Launceston Magistrates Court heard previously during a two-day hearing.

Morrison, of Somerset, estimated during evidence that he drank 15 beers between home, Hotel New York and Lloyds Hotel in Launceston on April 24, 2014, and said he had no memory of leaving Lloyds, nor the rest of the night.

He arrived at the LGH Emergency Department at 4.13am and had an equivalent blood-alcohol concentration of about 0.2 at 4.50am, having first come to the attention of ambulance paramedics after he was knocked unconscious for some minutes at Lloyds about 3am.

Dr Lindsay Tyrrell had given evidence that he made the decision to sedate Morrison because he had a ‘‘duty of care’’ towards him and staff, while Morrison’s erratic conduct and evidence of head injuries led him to believe he might have had a bleed on the brain or skull fracture.

Magistrate Michael Brett, in a decision published on Friday, said he accepted the evidence of the policeman about Morrison’s conduct and that the officer was acting in the execution of his duty at the time.

But he said the previously calm Morrison had expressed aggressively and loudly that he did not want an injection when he saw hospital staff approach him with a needle.

‘‘The injection into his body of an unknown drug was a gross violation of his personal security and integrity and, viewed objectively, justified the use of commensurate force in self-defence,’’ Mr Brett said.

‘‘The fact that several persons were attempting to restrain him for the purpose of leaving him vulnerable to the injection increases the level of force that would be considered reasonable in the circumstances.’’

Mr Brett said those actions of Morrison were therefore lawful and he dismissed the charges of assaulting a policeman and using abusive language towards him.

However, he found Morrison guilty of earlier conduct on the night, being assaulting a paramedic ‘‘with a full-blooded kick’’ in the face and threatening the paramedic by saying he would kill him and his family.

This occurred in a moving ambulance which was taking Morrison to the LGH with a suspected head injury because his friends requested paramedics attend to him a second time after he had again lost consciousness.

Morrison had threatened to charge the paramedic with assault if he touched him.

Defence solicitor Steve Wright said his client had suffered a serious nose fracture, was unwell at the time and had no intention to harm anyone.

Mr Brett fined Morrison $700.