A neck mechanism for a mannequin comprises three or more joint units serially connected to provide joints for three or more rotational degrees of freedom (DOF). A rotational axis of a first DOF is configured to be aligned with a lateral axis of the mannequin. A rotational axis of a second DOF is configured to be aligned with an anterior-posterior axis of the mannequin. A rotational axis of a third DOF is configured to be aligned with a cranial-caudal axis of the mannequin. A bottom one of the joint units is adapted to be connected to a torso of the mannequin, and a top one of the at least three joint units is adapted to be connected to a skull. The mannequin may also have a skull connected to the top one of the joint units, and a trunk connected to the bottom one of the joint units. A system for simulating cervical spine motions is also provided.