Martin opened fire when his ramshackle farmhouse was burgled
Farmer Tony Martin has lost his High Court appeal against the parole board's refusal to allow his early release from prison.
He will now have to wait until the end of July, when he becomes automatically eligible for release.
Martin was originally sentenced to life three years ago, for shooting dead 16-year-old Fred Barras while he was burgling his home.
The sentence was reduced to five years on appeal, when his offence was downgraded to manslaughter.
Mr Justice Maurice Kay, sitting at the High Court in London, said there were no grounds for allowing Martin's challenge to the parole board.
Risk of violence
He said there had been an
"initial error of law" when the parole board turned down Martin's application, because they had not seen some reports.
They had since seen them and decided they made no difference, he said.
He also said the parole board was entitled to conclude from probation officers' reports that Martin was unrepentant and likely to reoffend if released early.
The probation officers who wrote the reports had given very detailed reasons why early release was not recommended, he said.
And a so-called secret document which was never disclosed to Martin's legal team - and which the judge considered in private - did not
"materially advance" Martin's case, he said.
Martin's spokesman Malcolm Starr said Martin would be "slightly disappointed" by the court's decision, although not particularly surprised.
'No risk whatsoever'
He blamed the probation officers involved for taking a personal dislike to Martin and writing a biased report.
And he said Martin believed he would have received fairer treatment "if he was a burglar".
As for the question of Martin's repentance, he said the farmer had shot Barras because he had been "overcome with fear", and was "no risk whatsoever" to anyone else.
"Mr Martin feels very sorry for the fact the whole incident happened, it's ruined his life as well, but he didn't start the problem."
His message to any burglars supposedly at risk from Martin was simply to keep away from the farm, he said.
Mr Martin feels very sorry for the fact the whole incident happened... but he didn't start the problem
Martin's spokesman Malcolm Starr
But founder of the national ex-offenders' charity Unlock, Mark Leech, who is
himself a former prisoner, said the ruling was right.
"Many, including me, have sympathy with
"But in reality Tony Martin is no different to any other offender who crosses
the line between legal acts on one hand and criminal conduct on the other.
"We don't have a death sentence for burglary in this country and we don't
want one either."
Martin is due to leave Highpoint Prison, Suffolk, on 28 July anyway, after serving two-thirds of his sentence.
The episode began in August 1999 when Barras, 16, of Newark, Nottinghamshire, and accomplice Brendon Fearon, 33, broke into Martin's remote, semi-derelict farmhouse in Emneth Hungate, Norfolk.
Martin, who was in the house at the time, opened fire with an illegally-held pump-action shotgun.
Barras died and Fearon suffered leg injuries.
The shooting ignited fierce national debate about rural crime, self-defence, and the right of householders to use force to defend their property against criminals.