The trial of Muammar Gaddafi's son Saif al-Islam will be delayed by five months to include any relevant testimony obtained via the interrogation of Libya's former spy chief who was arrested last week, the prosecutor general office said on Sunday.
Government officials said in August Saif al-Islam's trial on charges of war crimes - the most high-profile prosecution of a figure from his late father's entourage to date - was due to begin in September.
But the arrest on Wednesday of Abdullah al-Senussi, the former spy chief known as "Gaddafi's black box", has pushed that date back, postponing a trial a lawyer from the International Criminal Court (ICC) has already said is unlikely to be fair.
"We were ready to try Saif al-Islam this month but after bringing back Senussi to Libya, new information will come to light which will delay the trial for at least five months," Milad al-Zintani, lawyer at the prosecutor general's office, told a news conference.
Senussi was handed over to Libya by Mauritanian authorities on Wednesday after being captured in the West African state in March, triggering a tug of war between Libya, France and the ICC for his extradition.
The announcement from the prosecutor general's office comes amid criticism of the trials of other former Gaddafi officials by the Libyan Council on Freedom and Human Rights.
"The law usually supports justice, but we are now facing an exceptional justice system which lacks the basis of a fair trial," Mohammed al-Alagy, a former interim justice minister who now heads the human rights council, told reporters.
Without naming any specific cases, he said trials were being ordered while bypassing necessary legal steps to ensure suspects are treated fairly.
So far, former spy chief Buzeid Dorda has appeared in the dock, and on Monday former foreign minister Abdel-Ati al-Obeidi and former secretary general of the General People's Congress Mohammed Zwai will stand trial.
Libya's new rulers, who aim to draw up a democratic constitution, are keen to try Gaddafi's family members and loyalists at home to show the country's citizens that those who helped Gaddafi stay in power for 42 years are being punished.
Human rights activists worry a weak central government and a relative lack of rule of law mean legal proceedings - both for Senussi and for Saif al-Islam - will not meet international standards.
On Wednesday, rights groups called on Libya's government to hand over Senussi to the ICC where an arrest warrant for him remains in force.
In July, a war crimes lawyer who was detained in Libya for three weeks on spying allegations said her experience had shown it was impossible for Saif al-Islam to get a fair trial in his home country.