Celtic manager Ronny Deila has hit out at Scottish Football Association disciplinary rules after Aleksandar Tonev's seven-match ban for racist language was upheld.
Tonev was described as neither a credible nor a reliable witness by an SFA-appointed judicial panel in a report that was published following the failure of his appeal.
The report revealed Aberdeen defender Shay Logan had accused Tonev of calling him a "black c***" during a Scottish Premiership match on September 13 and the panel found the on-loan Aston Villa winger guilty after describing the Dons player as an "impressive witness".
The SFA's disciplinary rules, like civil court cases, do not require that guilt be established beyond reasonable doubt, unlike criminal cases.
The criteria for finding Tonev guilty was summed up in the report as "it is more likely than not that the subject of the complaint committed the act of misconduct alleged''.
But Deila, whose side face Dundee United tomorrow, feels more proof was needed - no one else heard the offending words, although Logan quickly told others.
The Norwegian said: "You can't judge a person on word against word, in my opinion. You will never do that in any real court.
"There is no proof and we still believe him. We will continue to do that when we don't have any other proof. You call another person a racist just on a word? I can't understand this happening.
"For me, if you're going to judge someone you need real proof. Because a Bulgarian guy, with not very good English, is going to defend himself? Not so easy."
Celtic vowed to address issues raised in the proceedings with the SFA but there appears to be no recourse for challenging the decision again.
"I don't think there is any possibility to go further," Deila said.
"We have to take the penalty but we still feel it is not right and we believe Aleksandar in full."
Meanwhile, Deila insisted there had been no approaches for Kris Commons or Virgil van Dijk but confirmed he had taken 22-year-old Everton midfielder Francisco Junior on trial this week.
The Guinea-born player was previously with Benfica and Manchester City and had a loan spell under Deila at Stromsgodset.