(CNN) -- The daughter of ousted Libyan strongman Moammar Gadhafi is pressing U.N. war-crimes prosecutors to investigate the October deaths of her father and one of her brothers during Libya's civil war. In a letter released Tuesday, Aisha Gadhafi's lawyer questioned whether the International Criminal Court has taken any steps to investigate the deaths of Gadhafi and his son Mutassim. The attorney, Nick Kaufman, said both "were captured alive at a time when they posed no threat to anyone," only to be "murdered in the most horrific fashion" after their capture. "If your office is not currently investigating the aforementioned crimes, could you explain why and what steps have you taken to ensure that the Libyan authorities are, themselves, investigating the matter properly and in accordance with international investigative standards?" Kaufman wrote to the court's chief prosecutor, Luis Moreno-Ocampo. There was no immediate response to the letter from the prosecutor's office. Gadhafi ruled Libya with an iron fist for nearly 42 years before being overthrown in August. Libya's transitional government said he was killed in the cross-fire between its fighters and Gadhafi loyalists after he was captured in his hometown of Sirte on October 20. The office of the U.N. High Commissioner for Human Rights and two major human rights groups called for an investigation into Gadhafi's death in October. An autopsy determined the 69-year-old fugitive died from a gunshot wound to the head, but the pathologist who performed the procedure would not reveal whether the wound was inflicted at close range or from a distance. And the bodies of the ousted ruler, his son and his longtime defense minister were put on display in a meat-market refrigerator for several days before being buried -- a step Kaufman said was "in complete defiance of Islamic law." "The images of this savagery were broadcast throughout the world, causing my client severe emotional distress," Kaufman wrote. Kaufman questioned whether the ICC was investigating the NATO airstrike that preceded Gadhafi's capture, whether it had received any details of the autopsies and why it did not dispatch an independent expert to the post-mortems. Aisha Gadhafi fled to Algeria along with several other family members as the regime crumbled in August. She is a lawyer who assisted in the defense of ex-Iraqi dictator Saddam Hussein, who was hanged in 2006, and a onetime U.N. goodwill ambassador. Gadhafi's son and top aide, Saif al-Islam Gadhafi, was captured in November, Libyan authorities said. Senior Libyan military officials said they believed he was trying to make his way to neighboring Niger, where a brother, Saadi, was granted asylum. Gadhafi's youngest son, Saif al-Arab, was reported killed in a NATO airstrike in April. And son Khamis Gadhafi, who led an army brigade blamed for the massacre of prisoners in a warehouse outside Tripoli, was killed in a late-August battle in northwestern Libya, rebel commanders said.