The court increased Hagai Amir's prison sentence from 12 to 16 years.

Accomplice Dror Hadani's seven-year sentence on charges of conspiring to kill Rabin remains unchanged. His lawyer, Zion Amir, said he would be released in about six months, after having his sentence reduced one-third for good behavior.

After Yigal Amir was led into the prisoner's dock of the Supreme Court, reporters asked him whether he regretted the fact that he had killed Rabin.

Amir did not speak. But in response to the questions, he offered a lopsided smile with the right side of his mouth. In response to the same question, his lawyer, Shmuel Fleishman, later said, "I have not heard him express regret. He believes that what he did was the right thing."

The court ruled that Yigal Amir had not been sufficiently punished for his plans to kill Palestinians.

"His role in initiating the conspiracy to carry out terror attacks against the Arab population of Judea and Samaria was much greater than Hagai's," wrote Justice Yaacov Kedmi in the main opinion.

"His role in the mounting of a silencer on Hadani's Uzi submachine gun was much greater than Hagai's. The punishment of five years imposed on Yigal for the crimes of which he was convicted regarding this count does not sufficiently express the severity of the deed, nor is it proportionate to the sentences handed down to Hagai and Hadani."

As for Hagai Amir, Kedmi listed all the crimes of which he had been found guilty — including his role in his brother's preparations to kill Rabin, the fact that he and his brother reconnoitered the area around Rabin's home, and his repeated requests to the army to give him an M-16 rifle that Yigal Amir intended to use to shoot Rabin from long distance.

"The 12-year jail sentence given to Hagai does not give appropriate expression to the multiplicity of crimes and the aggravated circumstances in which they were carried out," wrote Kedmi. "It does not have a sufficient deterrent effect to prevent similar acts, the danger of which to the well-being of the state and public security is obvious."