Mr Ninn-Hansen, 71, the grand old man of the Conservative Party and Mr Schluter's mentor, is accused of breaking the law by ordering a halt to family reunifications for Tamil refugees from Sri Lanka in 1987. Prosecutors describe the proceedings, the first in Denmark in 84 years, as an ordinary criminal trial. The defence says it is the last round in a political power-game.
Mr Ninn-Hansen denies breaking the law, saying he was carrying out the implied wishes of his own minority centre-right cabinet and the opposition Social Democrats.
A final ruling by the panel of 12 Supreme Court judges and 12 lay judges appointed by parliament is expected in the second half of the year. He could face a fine or up to two years in jail.
The crux of the case is about the supreme power of parliament and adherence to Lutheran values such as following the rules and always telling the truth. 'Try to look away from refugees and immigration policies. This case is not about Tamils. It is about the law applying to all citizens, even to justice ministers,' the prosecutor, John Petersen, said as proceedings started.
Mr Ninn-Hansen says that because he was anticipating tighter legislation on immigration he had asked officials in his ministry to put Tamil cases on 'hold' within the boundaries of what he described as woolly immigration laws. The prosecutors maintain the law gives refugees an unambiguous right to have their families join them.
An influx of Tamils fleeing the civil war in Sri Lanka in 1987 coincided with widespread sentiment in Denmark that immigration in general and family reunifications in particular had to be curtailed. A parliamentary majority in favour of tougher immigration laws never materialised, and the halt to Tamil reunifications was revealed by the parliamentary ombudsman in 1989.
Mr Ninn-Hansen, H P Clausen, who succeeded him as justice minister, and Mr Schluter himself were accused of misleading parliament in attempts to cover up the scandal. Mr Schluter resigned early last year after a 30-month judicial inquiry.