A boy who stabbed his foster mother to death had fought with other pupils at his school and been teased about his foster background, an inquiry has heard.

The boy - who was aged 13 at the time - is said to have suffered mental turmoil in the days before the killing after being shunned by his friends and told his real father was dead.

Dawn McKenzie, 34, was stabbed to death in her home in Hamilton, Lanarkshire, in June 2011 after the boy had been placed with her and her husband Bryan.

He was jailed for seven years in 2012 after admitting culpable homicide on the grounds of diminished responsibility.

Child psychologist Dr Eleanor Kerr, 59, who interviewed him in February 2012, told a fatal accident inquiry into Dawn's death that the boy's school friends had distanced themselves from him and failed to turn up at his 13th birthday party.

She said: "They were getting irritated with him, he was getting into a few fights again. They said he had headbutted a boy in school.

"There had been name calling about his mother and teasing about him being in foster care.

"The birthday party to me means he wasn't included in that social peer group any more and that was a rejection."

Dr Kerr said the boy had become anxious after confronting his birth mother about the identity of his father and was told he was a "short, fat man" who was dead.

She added: "He was also hearing more information about his biological father and expressing angry feelings about his mother.

"It was churning up his mental state. I think it's safe to conclude he would be emotionally unsettled at the very least.

"The theory is that there must have been something that triggered overwhelming emotional pain.

"It's likely that this was memories which related to how he was feeling at that time. He was very concerned about not being listened to."

The probe had earlier heard the boy told doctors he heard a voice in his head telling him to get a knife and 'hurt Dawn' after arguing with her and her husband and having personal belongings confiscated.

Dr Kerr said: "He said they couldn't take them off him because they were his belongings and his mum had given it to him.

"He felt angry that things his mum had given him were removed and said he had never felt so angry in his life. He heard the front door close and he knew Bryan had gone out.

"He said he started to feel as if he was on the ceiling watching himself and a voice in his head was telling him to get a knife from the kitchen and hurt Dawn.

"After he came to himself he said he realised he had done something awful and he ran out of the house."

The inquiry, which is being held in Motherwell before Sheriff David Bicket, continues.