A mother and son who acted with what a judge described as "venom and a desire for revenge" when they murdered a man who ran across their land have been jailed.
Carol Dawson, 72, and her son Scott Dawson, 41, pursued a bitter vendetta against the "essentially harmless" marathon runner Gary Dean.
The 48-year-old was shot in the back with an air rifle and repeatedly beaten with rocks and branches in a pre-meditated attack which the mother and son plotted in response to his use of their land.
A judge at Sheffield Crown Court said that the killing had been carried out with "brutal determination".
A jury heard how the pair had been in a furious dispute with Mr Dean, who is believed to have been on the autistic spectrum, after he started using a footpath by his home in Silkstone Common, Barnsley, which had been purchased by the defendants.
The mother and son attempted to have their victim prosecuted, and spread malicious, false rumours about him, including that he had attempted to lure children into the woods with him, prosecutors said.
On the morning of September 6 last year, the pair lay in wait and, after Mr Dean's wife had gone to work, carried out the killing.
They showed no reaction on Monday as they were both handed life jail terms, having been convicted on Friday of murder after a five-week trial.
Scott Dawson, of Allotts Court, Barnsley, was told he would serve a minimum of 31 years, while his mother, of Stonewood Grove, Barnsley, will serve a minimum of 26 years.
Sentencing the pair, Judge Jeremy Richardson QC said: "It is a reasonable inference that it was you, Scott Dawson, who executed the killing and took the lead. It is also a reasonable inference that you, Carol Dawson, fully participated in the killing by encouraging and facilitating the execution of it.
"The murder of Gary Dean was carried out with brutal determination.
"I have little doubt that you both encouraged the other to act. The venom within each of your characters permeated the other to make a truly toxic and dangerous situation."
The judge said that Mr Dean's condition meant that he had been a vulnerable target, and that he had been an anti-social character as he found interactions with others challenging.
He added: "Instead of trying to understand his problems and approach them as others had, you commenced a vendetta.
"This involved peddling truly unpleasant rumours and starting a process of targeted intimidation against him."
Jurors heard how the vendetta against Mr Dean started in late 2016, when his wife Caroline woke one morning to find her car and house daubed with graffiti saying "stay away Baz", "paedo" and other offensive comments.
Mrs Dean, a headteacher, explained in her evidence how she and her husband were regularly followed and threatened, describing how four youths burst into their home, injuring both of them.
She also said that her school once received a letter claiming she should not be allowed to work with children as Mr Dean had attempted to lure youngsters into the woods with him.
She said that a local authority safeguarding inquiry found nothing to support the accusation, adding that her husband was never arrested over anything untoward relating to children.
The trial heard how the dispute over the path involved the Dawsons securing a restraining order against Mr Dean after they complained to police about him, saying he was damaging their property.
A "stay away" sign had been posted on a stile leading to the path, the court heard.
The judge said that Mr Dean had been a warm, kind and loved man, adding: "You both, on the other hand, were filled with venom and a desire for revenge for what you, inaccurately, perceived was police inaction.
"You lost all sense of proportion and became envenomed with a desire for revenge when you thought nothing was being done to prevent this essentially harmless man from behaving in what was at worst in 2018 a mildly anti-social manner."