A man who tried to silence vulnerable witnesses when his son was facing a murder charge has had his jail term slashed by Appeal Court judges today.

Thomas Robert Harrison, who urged one witness to "tell a pack of lies" to police and paid for 750-worth of hotel "board and lodging" for another, will also be more than £23,000 better off when he leaves jail after the judges overturned a prosecution costs order against him.

Harrison, described as devious and arrogant, brought pressure to bear on witnesses in a bid to see his son, Lee Harrison, get away with his part in the killing of Middlesbrough market trader Kalvant Singh.

Lee Harrison, who had to be extradited from Jamaica to stand trial in November 2004 pleaded guilty to manslaughter and was jailed for nine years.

But his 63-year-old father got a ten-year sentence after he was convicted the following month at Newcastle Crown Court of conspiring to pervert the course of public justice.

Appeal Court judges dismissed arguments that Harrison's conviction was unsafe but went on to cut his jail term to six years.

Mr Justice Nelson, sitting with Lady Justice Hallett and Mr Justice Jack, also overturned an order that Harrison must contribute 23,433 towards the costs of his prosecution.

The judge said it was "without question a serious case" in which Harrison had conspired to interfere with the course of a murder trial.

However, Mr Justice Nelson said there were doubts as to whether Harrison used any violence against the witnesses and, if he did so, it was only "relatively minor".

The judge added: "We conclude that ten years in these circumstances was excessive.

"A conspiracy to interfere with a murder trial in a climate of increasing interference with the justice system, however, requires a deterrent sentence.

"We consider that a sentence of six years imprisonment would meet the justice of the case."

Although the Crown Court judge had described Harrison as a man of "ample means", Mr Justice Nelson also overturned the prosecution costs order, saying there was no proper evidence of means on which it could be based.

When sentencing Harrison, the trial judge, Peter Fox, QC, said it was an attempt to pervert the course of justice of "the most serious type".

He had "planned and controlled" the campaign to interfere with the trial and Judge Fox condemned Harrison's "inherent deviousness and arrogant disdain for officers of the law and the grip he had on others".

Two other Middlesbrough men, Thomas Petch and George Coleman, were jailed for life after being found guilty of Mr Singh's August 2001 murder.

Their challenges to their convictions were dismissed by the Appeal Court last year.

Another man Jonathan Crossling, known as "Bam Bam" had to be extradited from Spain and was jailed for 18 years in June 2003, having admitted manslaughter, four counts of causing grievous bodily harm with intent, and one of aggravated burglary.

The men were said by the prosecution to have engaged in an orgy of violence sparked by a "turf war", in which Mr Singh was hurled to his death from a window in Errol Street, Middlesbrough.

Dealing with Harrison's appeal yesterday, Mr Justice Nelson said he had approached one female witness on three occasions, amongst other things urging her to "tell a pack of lies" to police and change her story or be "sorted out" by thugs.

Harrison was also said to have paid 750 for another witnesses' hotel board and lodging in a bid to put his son in the clear.