Throughout 1955 and 1956 the Special Branch conducted a series of raids on offices and private homes of hundreds of opponents of apartheid. Documents, letters, pamphlets, even pieces of clothing were seized in preparation for a show trial.

Finally, early on the morning of 5 December 1956, hundreds of policemen throughout the country descended on the homes of leaders of the Congress Alliance and arrested them. One hundred and fifty-six people – 104 Africans, 23 Whites, 21 Indians and 8 Coloureds – were charged with high treason, a capital offence in South Africa.

While the case was remanded against most of the accused, 30 of them sat in court almost daily for four-and-a-half years, their normal lives disrupted, and had to listen to an endless recital of long documents, garbled reports of ANC meetings and fabrications by bought informers. The Treason Trial was the main attack on the Freedom Charter, but in the end the court acquitted and discharged all the accused.

The trial was held in two stages, a preparatory examination in a magistrates court which was to determine if there was sufficient evidence to warrent a trial, and then, if evidence existed, a trial by the Supreme Court. The preparatory examination of the case lasted over a year until January 1958. As a result chargess against 61 of the accused were dropped.

The main trial lasted until 1961, when all of the defendants were found not guilty. During the trials, Oliver Tambo went into exile. Some of the defendants were later convicted in the Rivonia Trial in 1964.