Villagers in Kampong Speu province have alleged that sugar plantations operated by Ly Yong Phat have pushed them off their land.
The Cambodian government is facing more accusations it has cracked down on freedoms of expression and the media in the past years.
Four men including a human rights worker received lengthy jail sentences in Takeo province Monday.
She also called for sufficient lawyers to provide legal services to the people.
Other court observers say the government lacks the political will to reform the judiciary or overcome Cambodia's culture of impunity.
Adhoc investigators say at least 26 prisoners have died across the country in the first six months of the year.
A leading organization met with US policymakers last week to discuss more effective use of aid money for rights and democracy.
The courts have come under increasing scrutiny in recent years as they’ve shouldered criticism for political bias and corruption.
Since 2008, readership has fallen by as much as a half at some opposition-aligned papers.