The two presidents were addressing a rally of thousands in Tbilisi from behind a bulletproof barrier when a grenade, wrapped in a cloth, landed about 100 feet away. It did not explode; investigators said it apparently malfunctioned. No one was hurt.
Arutyunian acknowledged that he threw the grenade in the direction of the tribune and said that he would try again to kill Mr. Bush if he had the chance.
He has refused to testify before the court and demanded the presence of rights monitors.
"The verdict is preordained," he said Monday. "I demand that the international organization Human Rights Watch be present."
Arutyunian, 27, has been unemployed save for odd jobs since leaving school early. He lived with his mother Angela, who sells plastic bags at a Tbilisi market.
Investigators say they found explosives, toxic compounds and detective literature including Day of the Jackal, a book about an assassination attempt against French President Charles de Gaulle, in the basement of Arutyunian's residence. Arutyunian also had a Kalashnikov assault rifle and a Russian military uniform, though there is no record of his serving either in the Georgian or Russian military.
Interior Minister Vano Merabishvili told journalists that Arutyunian "acted as an individual terrorist. He was not tied with the special services of any other country."