Speaking on this issue, Dr. Hatemal-Haj, a associate professor of Fiqh said:
“There is no indication in the Qur’an or authentic Sunnah that anyone is infallible except the messengers and prophets. They are completely infallible regarding the transmission of the revelation. They are also immune to falling into the enormities the people of the book have attributed to them. That is because they were meant to be role models for the people and Allah would not send such defective role models who commit disgraceful sins like incest.
As for the imams of the shi`ah, they are great righteous descendants of the Prophet (peace and blessings be upon him), and they never claimed infallibility to themselves, nor will you be able to find any proof in the revelation on that claim.”