Judge Eben Jordaan rejected the suggestion by the 22 accused that police informants, who were used as State witnesses, had acted as provocateurs.
He said the accused were not put off when they realised that there were informers in their ranks.
Some of them had in fact continued with the plan to overthrow the ANC government and had planted more bombs, which had caused a woman's death and had caused damage worth millions of rands.
This was after the first few trialists had been arrested and while some were still on the run from the police.
Additional bombs planned for Pretoria and Johannesburg were prevented only when the police arrested the last three accused late in 2002.
The State's allegation of an alleged coup conspiracy was not based only on the planning document known as "Document 12", but on numerous other documents and the totality of the evidence.
Document 12 was found on the computer of the first person arrested and the deduction was inevitable that he was its author.
Jordaan rejected argument that using former alleged co-plotters as State witnesses, testifying in return for possible indemnity from prosecution, was unconstitutional.
He also rejected claims that two of the accused were "forced" to make admissions late in the trial.
Although the accused claimed to have believed they were involved in a legitimate war against a "racist regime", Jordaan said they could not have believed that civilian targets, such as a mosque, were legitimate targets.
The 22 accused in the treason trial are accused of forming an organisation and recruiting others to overthrow the existing government, and of committing serious, violent crimes in the process.
They are also accused of the large-scale manufacture of explosives and of causing a series of bomb explosions which killed a person and caused damage worth millions of rands.
The accused denied all the charges at the start of the trial. Many of them changed their versions and made certain admissions only many years later.
A total of 194 witnesses have testified for the State, and many State witnesses spent months in the witness box.
Jordaan said he still had to prepare a part of his judgment and that he might take longer than the expected three weeks to deliver a summary of his judgment.
He will continue reading a summary of his judgment, against each of the 22 accused, on Wednesday.