Is the female doctor considered responsible for the infant's death if she did not pay attention—as she claimed—to the laboratory technician's alert about the availability of a different blood type than what was requested, even though she performed her duty perfectly?

There is no sin upon one who causes accidental death, due to the lifting of accountability for error and forgetfulness. However, worldly responsibility is not lifted, so blood money (diyya) is obligatory by consensus. Scholars differed regarding the obligation of expiation (kaffarah (definition)) into two opinions: The Hanafis do not consider expiation obligatory, while the Malikis, Shafi'is, and Hanbalis consider it obligatory. As for determining who caused the death, that requires consulting experts and investigating the incident.