“The new Libya should be about giving prisoners and detainees their rights,” Mr. Abrahams said. “They should give him the rights that his father denied to Libyans for so long. That would be a legal and moral victory for the new Libyan authorities, to say, ‘We will not behave like you.’ ”

Image Seif al-Islam el-Qaddafi Credit... Ammar El-Darwish/Reuters

Though friends and supporters have not been allowed to visit Mr. Qaddafi, several high-ranking officials in Libya’s interim government have been to see him. They include the country’s general prosecutor, a former justice minister and Prime Minister Abdel Rahim el-Keeb, whom Mr. Qaddafi dismissed as “the so-called prime minister” during their meeting, Mr. Abrahams said.

Rumors have circulated about the treatment of Mr. Qaddafi at the hands of the Zintan fighters, who were believed to be resisting efforts by the central government to take over his case. The office of the general prosecutor in Tripoli, Abdelaziz al-Hasadi, has jurisdiction, and gave Human Rights Watch clearance to visit Mr. Qaddafi. Mr. Abrahams was then taken to Zintan, where militia commanders appeared to be cooperating with the central authorities.

Mr. Abrahams said the arrangement showed how the situation in Libya was still evolving. “It is not accurate to say he is being held by a militia outside of government control, although it is not true that he is in a prison directly controlled by the government, either,” he said.

Officials said the prosecutor planned two parallel investigations of Mr. Qaddafi, one into corruption before the Libyan revolution and the other into crimes committed during the conflict. The first is under way, they said, but it was not clear when the second would begin. Abdul Majid Saad, Libya’s deputy general prosecutor, said Mr. Qaddafi would be allowed to have a lawyer as soon as he could hire one, though considering the way his family is viewed in the country, finding a willing lawyer may not be easy.