The criminal Slitheen family were convicted of high treason by order of the High Council of Raxas Prime. (TV: The Gift)
In 4000, Mavic Chen and his SSS security chief Karlton were found guilty of high treason when a message recorded by Marc Cory revealed that the two had been conspiring with the Daleks. The sentence was execution, although Chen was already dead when Senator Diksen arrested Karlton. (PROSE: The Mutation of Time)