A man accused of stabbing his mother to death has paranoid schizophrenia and was experiencing a psychotic episode at the time of the incident, a court has heard.

Shaun Emmerson, 51, climbed on the roof and called 999, admitting that he had carried out a “violent attack” on his mother Christine, 71, at their home in Kirk Close, West Ashby, Lincolnshire, on August 3 last year.

Emmerson has been deemed mentally unfit to stand trial or enter a plea to murder, so a trial of the facts is being held in his absence at Lincoln Crown Court, at the end of which the jury will decide whether he committed the act or not.

The court heard on Wednesday that three psychiatrists have independently assessed Emmerson and agree he has paranoid schizophrenia and experiences delusional thoughts and beliefs.

In a 999 call Emmerson made at 12.31pm, after allegedly stabbing his mother 26 times in the neck, he could be heard telling the operator to send armed officers to the scene to “put me out of my misery” and claimed the “Department of Justice have been torturing me for the last 20 years”.

He also thought he could hear his “neighbours through the walls” who were saying they wanted to kill him in a “painful” way, that everyone was “evil” and he was afraid that someone would “attack” him in his sleep, despite reassurances from his parents that he was safe.

Emmerson had been on antidepressants for around 20 years, his brother Daniel told the court on Tuesday, and did not like to leave the house or his bedroom because he could not cope with seeing strangers.

He said his brother would often barricade the door to his bedroom at the home he shared with Christine and his father David with a weightlifting bar and had recently become interested in helping charities online, donating money and taking part in challenges by walking laps around the garden or up and down the stairs.

Daniel Emmerson said he did not know how to deal with what had happened to his “caring” mother, who did “everything” for his brother, adding: “I have never seen him become violent or threatening to anyone.

“There has been no indication he would hurt anyone other than himself as he has mentioned suicide over the years.”

A statement from David Emmerson said his son would often stay in his bedroom playing online poker tournaments but was becoming more concerned in the weeks before his wife was killed that he was in a “bad place” as he was spending more time in his bedroom and would obsessively watch and record the news.

He said his son did not like his mother leaving him in the house alone and had admitted to him that he “may have missed a few” of his prescribed tablets.

The Wednesday night before Mrs Emmerson was killed, Shaun Emmerson had come down to “say goodbye” to his mother as he feared someone would be coming to kill him that night, but his parents reassured him he was safe.

Prosecutor Christopher Donnellan KC told the jury that by looking at all the evidence, the “only sure conclusion is that [Emmerson] did the act”.

Referencing the 999 call Emmerson made, in which he said he had stabbed his mother and correctly told the operator his name, address and date of birth, as well as his mother’s date of birth and where his father worked, he said: “Although he was quite ill, it did not stop him understanding what he was doing and talking about what he was doing even though he had those type of persecutory thoughts.

“He had background thoughts of other people trying to get him, but notwithstanding that he had those thoughts, the other bit of him is able to function normally.

“He wasn’t somebody who was hallucinating, he wasn’t having voices instructing him to do or say anything, so when he does speak, it is reliable.

“He made a rational decision to call 999. It is a circumstance that logically called for help and he did call for help.”

Clive Stockwell KC, who is representing Emmerson, said the jury needed to consider the evidence thoroughly to decide whether he killed his mother.

He said: “His brother says he has never seen Shaun be violent or aggressive towards anyone. There has been no indication he would harm anyone.

“His father said the relationship between Shaun and Christine was good. There is no suggestion there was hostility or the threat of violence. He is of previous good character.

“You are entitled to take that into account as to whether he killed his mother.”

He added: “All we invite you to do is consider this case with the care you have so far and keep an open mind and question the evidence.

“If you conclude he did kill Christine Emmerson, having been thorough, having been clinical and objective, then this system can require no more of you.

“If you adopt and take the care we know you will, your answer will be the right one.”

The jury is expected to begin its deliberations on Thursday morning.