In a move described by Cambodian observers as a blow to free expression in the country, the Supreme Court upheld on 3 June 2010 a lower court's guilty verdict in the defamation case against opposition legislator Mu Sochua.

Cambodia's High Court also upheld the lower court's decision to fine her 16.5 million Riels (or almost US$4,000).

The opposition lawmaker described the ruling as "a travesty of justice", adding that she was found guilty "of a crime I did not commit."

The case stemmed from a defamation case filed by Mu Sochua against Prime Minister Hun Sen early last year after he referred to her in a speech as "cheung klang" or "strong legs", a derogatory term in Cambodia.

Administration lawmakers then moved to strip Mu Sochua of her parliamentary immunity, thus paving the way for the prime minister to file charges of defamation against her. Meanwhile, the court dismissed the defamation case filed by Mu Sochua.

In August 2009, the Phnom Penh Municipal Court found the former minister of women's affairs guilty of defamation and ordered her to pay almost US$4,000 in fines. On 28 October that year, the Court of Appeal upheld the decision. Mu Sochua filed an appeal with the Supreme Court on 10 November 2009.

The Sam Rainsy Party (SRP) legislator said she would rather go to jail rather than pay the fine. "That’s been my position from the beginning," she told the "Phnom Penh Post". "I have not committed any crime. My conscience is clear."

She added that the defamation case is not just about her. "The Cambodian people are living in fear, and it is time to stand up," she said. "This is not about my case – it’s about the national interest."

SRP spokesman Yim Sovann said the party will support Mu Sochua's plans.

According to the "Phnom Penh Post", the Cambodian Centre for Human Rights (CCHR) released on 1 June 2010 a legal analysis of the case, stating that the lower courts "had failed to uphold Mu Sochua’s right to a fair trial and ignored her right to freedom of expression, which is guaranteed by the Constitution".

Political observers said Mu Sochua's case is a test case for the Cambodian judiciary.

"It will be a crushing defeat for freedom of speech if the result goes against Mu Sochua," Hang Chhaya, executive director of the Khmer Institute for Democracy, said a day before the Supreme Court's decision.

After the trial, Mu Sochua and her supporters from the opposition Sam Rainsy Party marched to the venue of the Cambodia Development Cooperation Forum, where foreign donors are planning to pledge US$1 billion to Cambodia. However, anti-riot policemen blocked the path of the lawmaker and her supporters.