Paul "Jock" Palfreeman was convicted last December of fatally stabbing one man and wounding another during a street brawl in the Bulgarian capital, Sofia.
Palfreeman, 23, argues that he acted in self-defence after intervening to prevent an attack by the two Bulgarian men on a group of Roma, or gypsies.
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The Sofia Appeals Court on Thursday moved the appeals hearing to Novomber 11, spokeswoman Borislava Radoeva said, to allow defence lawyers to bring new witnesses to testify in court.
Palfreeman has been in custody since the December 2007 attack.

