Final answer:
After Ayatollah Khomeini's death in 1989, the new Supreme Leader was chosen by the Assembly of Experts, with amended qualifications that permit a council of theologians to assume the role if no single qualified leader is available.
Step-by-step explanation:
The leadership transition in Iran after the death of Ayatollah Khomeini in 1989 marked a significant change in how the Supreme Leader was selected and the qualifications needed for the role. His successor, Ayatollah Ali Khamenei, was chosen by the Assembly of Experts, an elected body of clerics knowledgeable in Islamic law, a process that reflects the country's shift to an Islamic Republic after the 1979 revolution.
The qualifications of the Supreme Leader changed as well; previously, the position required being a leading Mujtahid, a scholar with deep proficiency in Islamic jurisprudence, but after Khomeini's death, the constitution was amended to allow a council of lower-ranking theologians if no single qualified candidate was evident.