A man who thought his parents were ‘demonic entities’ killed his mother as she reported him to police for trying to poison his father.

Thomas Fraser stabbed Miriam MacDonald, 52, in the neck while she was on a 999 call on June 1 last year.

The 31-year-old had earlier spiked a can of juice his father, Ian MacDonald, 55, had been drinking. Fraser also turned the knives on Mr MacDonald before fleeing the family home in Inverness after brave neighbours stepped in to try to help the couple.

Mrs MacDonald died in hospital a short while later. Fraser was later traced by police and made a string of ‘disturbing’ remarks including: ‘I am Lucifer’.

He had faced charges of murder and attempted murder as he appeared in the dock at the High Court in Glasgow.

But, Fraser was acquitted after prosecutors accepted he was not mentally competant at the time. Fraser appeared in court having been brought from the State Hospital at Carstairs.

Psychiatrists concluded Fraser was suffering from a mental disorder and did not appreciate the ‘nature or wrongfulness’ of his conduct. The hearing was told Fraser believed his parents had been killed and taken over by a ‘demonic entity’.

Prosecutor Graeme Jessop, KC, told the hearing that Fraser – who is a twin – lived with his parents after moving back to their home in Inverness in March 2023 having previously been studying for a PhD in Electronic Engineering at Heriot Watt University in Edinburgh.

He had previously been awarded a Master’s degree in the subject.

The court heard there had been a decline in his mental health at university. He was said to have become ‘reclusive’ on returning to Inverness.

Days before the attacks, Mr McDonald had been making a coffee using his Nespresso hot drinks maker when he discovered a ‘white residue’ on the edge of the water tank. Mr Jessop: ‘He suspected Thomas Fraser had potentially put some sort of cleaning substance into the coffee machine.’

Fraser was confronted by his parents, but he denied being responsible. Mr McDonald took a drink from a can of Pepsi he opened before leaving it unattended on a coffee table.

Mr Jessop: ‘Upon drinking from it, the contents tasted flat and had a chemical taste.

‘This caused Ian MacDonald to spit it out into the kitchen sink.’

Mrs McDonald dialed 999 with concerns Fraser had tried to poison his father.

Mr Jessop then told the court: ‘While Miriam MacDonald was still on the phone, her husband started walking out of the kitchen. He looked behind him and saw Fraser holding a knife in each hand. He then proceeded to lunge towards Mr MacDonald.’

The son initially slashed Mr MacDonald on the arm then stabbed him in the chest.

Mrs MacDonald screamed down the phone: ‘Oh, they are fighting. Oh my God, he had got a knife. Can you please come? He’s coming with a knife.’

Mr MacDonald managed to stagger outside into the front garden. Mr Jessop added: ‘While Miriam MacDonald was on the call to the handler, Fraser attacked her striking her on the neck with a knife.

‘She was still on the call to police when Fraser approached her and repeatedly stabbed her on the neck.’

Two neighbours heard what was happening – they armed themselves with a shovel and a golf club to chase Fraser away.

Mr Jessop said he was arrested and on being charged said: ‘Embarassing I did not finish the job.’

Donald Findlay, KC, defending, said: ‘He is a very intelligent young man, an outstanding career in prospect in government service in relation to radar and all sorts of research matters.

‘But, something terrible has gone wrong.’

Lord Mulholland adjourned the hearing until July for updated medical reports and Fraser will remain in Carstairs for treatment.