The murder charge against Australian Jock Palfreeman could be downgraded amid new evidence that he was in "a state of rage" at the time of the incident, Australian daily Herald Sun said.

Palfreeman has been charged with the murder of 20-year-old Andrei Monov and wounding a second man in a fight on December 28 2007.

Australian daily Herald Sun said authorities were considering a lesser charge after the woman who was with Palfreeman on the night of the murder, returned to Sofia and was interrogated by police.

The British woman, known only as Susan, had been drinking with Palfreeman and she fled the country the day after he was arrested.

Herald Sun said authorities confirmed she had come back and that she had given a detailed statement, although they would not say whether her return was voluntary or forced.

Palfreeman's defence lawyer, Stoiko Barborski confirmed that charges could be changed as further evidence was being gathered by police, Herald Sun said.

"It may now be proven he did it, but he may not have been in his right mind, unstable, at that time and not responsible for his actions, the charges could change" Barborski said, adding a decision would not be known for three months when the case would return to court.

He reiterated that his client had made no admissions of guilt before the courts, Herald Sun said.

If the charge would be downgraded, the maximum sentence could be 10 years in jail or possibly less if Palfreeman would plead guilty.