The appeals court reaffirmed on Saturday a 2003 verdict, finding Ali al-Jar Allah guilty of the 28 December 2002 assassination of Yemeni Socialist Party deputy secretary-general, Jar Allah Umar, during an Islamic political conference.
"I killed a man who did not want Islamic law to be in use," al-Jar Allah, in a blue prison suit, told the judge from behind the barred courtroom dock, his hands cuffed.
The court, however, acquitted six of al-Jar Allah's alleged accomplices in Umar's killing, all of whom earlier had received sentences of three to 10 years.
After the decision was read, al-Jar Allah took off his shoes and held them up towards the judge's face, a sign of contempt. He shouted "God is Greatest, God is Greatest" and warned, without elaboration, that "the court has itself to blame".
The conviction upheld against al-Jar Allah also included his involvement in a plot that killed three Americans at a Southern Baptist missionary hospital in Jibla, southern Yemen, two days after Umar's assassination, as well as forming a cell to buy weapons and kill local officials and foreigners.