The son of deposed Libyan leader Col Muammar Gaddafi, Saif al-Islam, has briefly appeared in court to face criminal charges and has been appointed two local lawyers.
The case relates to a visit last year from a lawyer from the International Criminal Court (ICC) who was accused of passing information to Mr Gaddafi.
Mr Gaddafi has also been indicted for war crimes during the 2011 uprising.
Both Libya and the ICC claim jurisdiction for that trial.
When asked whether he was in good health, Mr Gaddafi said that he was and gave a thumbs-up sign, the BBC's foreign editor, John Simpson, reports from Zintan.
Mr Gaddafi faces charges of complicity in exchanging information, obtaining documents that threaten national security and insulting the national flag.
Evidence was briefly presented at the hearing, including a pen with a camera in it and a watch, which the prosecution alleges were used in passing illicit information.
Representatives from local and international human rights organisations were also present at the hearing.
The trial has been postponed until 19 September.
In June last year, ICC lawyer Melinda Taylor and three other ICC staff were arrested and held for the three weeks after visiting Mr Gaddafi.
Ms Taylor was accused of clandestinely passing Mr Gaddafi a coded letter from a fugitive former aide, Mohammed Ismail.
The four were subsequently released to The Hague and are not expected to return to Libya to face charges.
The ICC said last year that it would investigate the allegations.
Mr Gaddafi has been held in Zintan since a brigade from the town captured him in November 2011.
His British lawyer John Jones described the detention to the BBC as "Libya's Guantanamo Bay" and said he had no plans to visit Mr Gaddafi in Zintan.