BAGHDAD. An Iraqi court yesterday sentenced Ali Hassan al-Majeed, the Saddam Hussein henchman widely known as “Chemical Ali,” to death by hanging for a 1988 gas attack that killed about 5,000 Kurds. Majeed, a cousin of Hussein’s who earned his nickname because of his use of poison gas, was convicted of crimes against humanity for an attack on the Iraqi Kurdish town of Halabja. He already faces death sentences in three other cases.