A pensioner found guilty of threatening behaviour after posting online about the assassination of First Minister Nicola Sturgeon is due to be sentenced.

William Curtis, 70, was convicted last month of sending threatening messages to Ms Sturgeon and of sending or causing a threatening message to be sent to former MSP Stewart Stevenson in 2019 following a trial at the High Court in Glasgow.

Jurors also found Curtis and another man, 60-year-old Philip Mitchell, assaulted and abducted a sheriff in a car park in Banff, Aberdeenshire, in June 2021.

Mitchell claimed he was performing a citizen’s arrest on Sheriff Robert McDonald and had lawful authority to do so, but Lord Weir, in his direction to the jury, said there was nothing supporting this on an evidential basis.

Curtis and Mitchell are due to be sentenced at the High Court in Glasgow on Friday.

During the trial, advocate depute Chris McKenna read out a Facebook post from an account in the name of “William Patrick Curtis” that was flagged to Ms Sturgeon’s office manager John Skinner on March 6, 2019.

It said: “We have reason to believe while it is my intention to citizens (sic) arrest her (Ms Sturgeon) to answer her treason, over the last three years, serious people who reel the abuse to the electorate by her criminal activities warrants assassination of her and sevreal (sic) of her ministers, on down to even civilians who work in all agenices (sic) who have repeatedly lied to the electorate and conspired with the First Minister.”

Curtis’s former partner, Alyson Gould, confirmed to the court during the trial that he had a Facebook account in the name of the aforementioned social media profile.

Mr Skinner was asked in court what was made of the phrase “warrant assassination of her”, and he told the jury: “To murder the First Minister.”

Curtis was found guilty of behaving in a threatening or abusive manner which was “likely to cause a reasonable person to suffer fear or alarm” by sending an email and posting messages on social media in which he made threatening remarks towards Ms Sturgeon on various occasions between February 27 and March 6, 2019.

He was also found guilty of sending or causing a threatening message to be sent to Mr Stevenson on March 9, 2019.

It had a link to a video relating to the murder of West Yorkshire MP Jo Cox.

The court heard a direct message was sent on Facebook to Mr Stevenson from a person called “Carole Curtis” which read: “Your turn is comming (sic) of that you can be sure.”

Jurors also found Curtis guilty of a fourth charge of behaving in a “threatening or abusive manner which was likely to cause a reasonable person to suffer fear or alarm” by posting “messages of a threatening and abusive nature” in October 2020.

Curtis had lodged a special defence of incrimination, claiming someone else committed the offence against Mr Stevenson, but this was rejected by jurors.

All of the offences occurred in Aberdeenshire.