Paul 'Jock' Palfreeman was convicted in December 2009 of fatally stabbing one man and wounding another during a street brawl in the capital Sofia.
The 24-year-old had argued he'd acted in self-defence while intervening to prevent an attack by the two Bulgarian men on a group of Roma, or gypsies.
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But the Sofia Appeals Court upheld the original ruling and Palfreeman will now launch a final appeal at the country's Supreme Court.
His father has told The Australian online the family may also consider taking the matter to the European Court of Human Rights.

