By Guy De Launey
BBC, Pnomh Penh
A Cambodian court has found the country's opposition leader guilty of two counts of criminal defamation.
Sam Rainsy has been an outspoken government critic
It sentenced Sam Rainsy to 18 months in prison for remarks he made about the leaders of the governing coalition.
Sam Rainsy has been in self-imposed exile since losing his parliamentary immunity from prosecution in February, and refused to return for the trial.
This week he called the proceedings a travesty of justice and questioned the judiciary's independence.
The opposition leader had accused Prime Minister Hun Sen of involvement in a grenade attack on an opposition rally eight years ago. And he claimed that the Funcinpec party leader, Prince Ranariddh, had accepted financial inducements to form a coalition government.
The court ruled there was no evidence to support either accusation.
The Sam Rainsy party is now in an uncertain position. Analysts say the leader's prolonged absence has weakened the opposition.
The party's secretary general recently resigned and support for Sam Rainsy among the diplomatic community has dwindled after he missed several projected dates for his return.
Human rights activists have criticised the use of defamation suits against opposition figures.
Two critics of the government are in jail awaiting trial after speaking out against a border treaty with Vietnam and several others left Cambodia after charges were brought against them.