At first glance it seems to be simply a numbers game: whether to try 5, 10 or more defendants for the deaths of an estimated 1.7 million people at the hands of the Khmer Rouge three decades ago.

But as a United Nations-backed tribunal prepares to hold its first trial hearing this month, the wrangle over numbers is reinforcing longstanding concerns about the tribunal’s fairness and independence.

The Cambodian government, critics say, is trying to limit the scope of the trials for its own political reasons, a limit that the critics say would compromise justice and could discredit the entire process.