QUICK and unusually lenient judgments are expected from the Medan Public Court, where a mass trial begins tomorrow for scores of men accused of participating in riots that swept through Sumatra's largest city in April. The trials have attracted international attention, not only from human rights organisations but also labour officials. Observers say the proceedings are likely to influence critical Indonesian trade negotiations with the United States. Lembaga Bantuan Hukum, the Indonesian Legal Aid Foundation, has assigned more than 30 lawyers to the defence team. A foundation spokesman disputed government reports of more than 80 defendants, saying 64 people, including labour leaders, were charged with crimes. US officials in Jakarta told the Sunday Morning Post the Indonesian authorities had shown extreme restraint following the aftermath of worker protests in mid-April. A Chinese factory owner was beaten to death and dozens of shops owned by Chinese were targeted during the unrest. Labour leaders in Medan and Jakarta said the 20,000 protesters were stirred into anti-Chinese violence by a ''third force'', alleged to be gangster elements acting in co-ordination with the corrupt local military. ''We're expecting that the trial will be quick, and the defendants will mainly be given sentences that cover time served,'' said one lawyer for the foundation in Medan. None of the defendants has been charged in connection with the murder. Officials with international labour groups in Indonesia pointed to several factors showing a softening of the Government's hardline stance against worker activity. None of the national leaders of the banned labour group that organised the protests has been arrested and more importantly, none of the defendants has been charged with treason or subversion under the law that virtually bans any worker union activity. And all defendants will be tried in public, rather than a military court. Meanwhile, US officials are in the final stages of assessing Indonesia's treatment of labour relations before an August deadline on the awarding of special trade benefits under the Generalised System of Preferences. Indonesia has benefited from low trade duties with nearly 15 per cent of its 1992 exports to the US entering duty free, according to documents at the US embassy in Jakarta.