The defence has argued there is no legal basis for the charges against her and on Thursday Kyi Win, a legal expert and the sole defence witness to appear in the case, told the court that the charge was unlawful.
The charge against Aung San Suu Kyi cites a 1975 state security law, not the more narrowly defined confinement order for her house arrest, he said.
The law refers to Myanmar's 1974 constitution, which was annulled when the military took power in 1988, with a new charter adopted last year.
Speaking to reporters later, Kyi Win, who is a member of Aung San Suu Kyi's National League for Democracy (NLD), said prosecutors seemed very unhappy at his testimony.
Defence lawyers had hoped to call two other senior members of the NLD to testify but the court rejected the move.
Aung San Suu Kyi, who turns 64 next month, has spent 13 of the last 19 years in detention.
Authorities earlier lifted her latest six-year period of house arrest but she remains in jail pending the court verdict.
The trial has drawn outrage from the international community, and opposition supporters and Western governments critical of Myanmar have labelled it a pretext for the ruling generals to keep Aung San Suu Kyi in detention beyond national elections it has scheduled for next year.
|International and regional criticism of the trial continues to mount [AFP]
The government says the vote will mark the culmination of Myanmar's "road map to democracy," but critics say the regulations surrounding the election mean it will only cement the military's continued grip on power.
Myanmar, formerly known as Burma, has been under military rule since 1962.
On Thursday Myanmar's foreign minister lashed out at what he called "foreign pressure and interference" over the trial, denying the trial had political motives and saying it was an "internal issue".
"It is not political, it is not a human rights issue. So we don't accept pressure and interference from abroad," Maung Myint said in the Cambodian capital Phnom Penh, where he is attending a summit of foreign ministers from the European Union and the Association of Southeast Asian Nations (Asean).
The joint Asean-EU forum later issued a statement calling on Myanmar to release all political prisoners.
The rare rebuke from Asean was a move away from the bloc's traditional policy of non-interference in members' internal affairs.