An animal rights activist was jailed for six months for contempt after threatening a director of an animal laboratory in court.
The incident happened after Keith Mann, from Poole in Dorset, was sentenced for organising a raid on the same lab.
The 38-year-old had just been given a 230-hour community punishment order for the offence of conspiracy to burgle.
He was passing the public gallery when he threatened Chris Bishop, a director at Hampshire's Wickham Laboratories.
Judge Richard Price reconvened the court and held a short trial after which he jailed Mann for six months for contempt of court.
Mann, of Buckland Road, who was jailed in 1994 for 14 years for carrying out a terrorist-style sabotage campaign against the meat industry, had earlier been warned he faced a jail sentence on Friday.
But the judge decided to give him a chance and handed down the community punishment order after hearing the defendant was a carer for his partner.
But as Mann left the court, he lent over Mr Bishop and said to him: "Your trouble has only just started, you will need to look under your bed," the court was told.
Sentencing Mann for contempt of court, Judge Price said: "I will not have people leaving my court saying that sort of thing.
"I do not want to make him a martyr, he's just made himself one."
Speaking after the hearing, Mr Bishop said: "I am extremely concerned about Mann's comment made to me, which was completely out of order, and threatening
behaviour like that shouldn't be allowed to go on inside or outside of court."
Mann had been found guilty of organising a raid on the laboratory on 13 December, 2003 , which led to 695 mice and documentation being stolen.
He claimed he believed the tests were for cosmetic purpose and therefore illegal in the UK.
A second defendant, Melvyn Glintenkamp, 42, of North Drive, New Milton, was also been found guilty at the trial of conspiracy to burgle and was sentenced to 150 hours of community punishment.