A defendant demanded a second opinion and then threatened to kill a High Court judge as he was convicted of murder today.
Daniel Breaks, 48, beat Simon Sutton then forced two teenage children to kick the dying man's body, Liverpool Crown Court heard.
Breaks then dumped Mr Sutton's body in an alleyway before heading to County Durham where he used a knife to force an elderly couple to drive with him to London.
The prosecution said Mr Sutton, 40, the boyfriend of Breaks' sister, was killed because Breaks suspected the victim had informed the police about an alleged blackmail attempt against a high street bank.
Breaks, of Halville Road, Allerton, Liverpool, denied murder, kidnap and false imprisonment and conspiracy to blackmail.
After more than four hours of deliberations the jury cleared Breaks of the conspiracy charge but unanimously found him guilty of murder and kidnapping.
Laughing, Breaks shouted from the dock: "Can I have a second opinion Your Honour?"
To which Mr Justice Openshaw replied: "No".
Minutes later, after being told he would be sentenced tomorrow, Breaks, now clearly agitated, shouted to the judge: "You suppressed the truth in this trial.
"I will escape prison and I will kill you."
As members of the jury gasped in shock, Mr Justice Openshaw said to them: "He is unlikely to have the chance to carry it out."
Outside court Mr Sutton's family branded Breaks a "monster".
The victim's brother, Mark, 39, said: "The jury have seen through his lies and now everybody can see Breaks for what he is, a monster who took my brother's life and tried to destroy my family."
The jury was told how vengeful Breaks flew into a rage with slightly-built Mr Sutton, who weighed under eight stone and was just 5ft 6in, and beat him repeatedly with a pool cue, on April 11 last year.
When Mr Sutton died in the early hours of April 12, Breaks made two children, who cannot be identified, carry the corpse upstairs.
Outlining the fatal attack, Tim Holroyde QC, prosecuting, told the jury how Breaks launched three separate assaults on Mr Sutton over several hours.
He said: "Breaks set about Simon Sutton once again, this time with increased ferocity.
"He hit him on the head, body and limbs with the weighted end of the pool cue, punched him and kicked him saying 'This is what happens to grasses'."
Breaks made his girlfriend and his sister and Mr Sutton kneel before him and forced Mr Sutton to beg him to stop.
Mr Holroyde said: "At the end of this stage of the attack Simon Sutton was lying half-on and half-off the sofa, apparently only semi-conscious.
"After another period of quiet, Breaks dragged him off the sofa on to the floor and began kicking and stamping on him, including on the head.
"Breaks called the two boys into the room to look at Simon Sutton telling them 'That's what you get when you grass'.
"He then ordered the boys about in a military manner, making them stand to attention and then telling them to kick and stamp on Sutton, which they reluctantly did.
"He also ordered them to slap their own mother because, he said, she too was a grass and again, through fear, they reluctantly obeyed."
Breaks "was clearly not at all troubled by what he had done," said Mr Holroyde.
After dumping Mr Sutton's body in an alley behind his home in Argyle Street South, Birkenhead, Merseyside, Breaks went to see pensioner friends Charles and Joy Heaps in Durham where he abducted and drove them to London at knife point after binding their wrists and taking their cash cards.
He forced the couple into their own car which he drove, drinking brandy "and brandishing the knife" to London - stopping to withdraw money from Mrs Heaps' bank account.
Breaks eventually stopped somewhere in north London, apologised, and left them in the car.
Breaks, who in 1989 was jailed for 14 years for causing death by reckless driving, was arrested on April 20.
During the trial he claimed two unnamed men attacked and killed Mr Sutton.
He said he could not name them because they had threatened to kill his sister.
It was also alleged during the trial that Breaks and the dead man's brother Jason Sutton, 28, were part of a plot to blackmail £300,000 from a branch of HSBC on Grey Street in Newcastle.
On March 22 last year a CD containing a recorded demand for cash was delivered to the bank but was left in a drawer and ignored.
The blackmailers also rang through another simulated ransom demand to a News of the World reporter who contacted Northumbria Police.
Sutton, of Rockville Street, Birkenhead, Merseyside, denied conspiracy to blackmail.
Along with Breaks he was cleared of the conspiracy allegations and released from the dock.
Breaks will be sentenced for the murder and kidnappings tomorrow.
Mark Sutton said: "It has been very, very difficult because one brother has been murdered and another has had to sit in the dock alongside the killer.
"But now Jason has been cleared and tomorrow Breaks will be jailed for a very long time.
"My mother and the rest of us can begin to grieve for Simon and re-build our lives."