Where necessary, hits should be checked by a trained fingerprint expert in order to ensure the accurate determination of responsibility under , the exact identification of the third-country national or stateless person and the exact identification of the criminal suspect or victim of crime whose data might be stored in Eurodac. Checks by a trained expert should be considered necessary where there is doubt as to whether the result of the comparison of the fingerprint data relates to the same person, in particular where the data corresponding to a fingerprint hit belong to a person of a different sex or where the facial image data do not correspond to the facial feature of the person whose biometric data were taken. Hits obtained from Eurodac based on facial images should also be checked by an expert trained in accordance with national practice, where the comparison is made with facial image data only. Where a fingerprint and facial image data comparison is carried out simultaneously and hits are returned for both biometric datasets, Member States should be able to check the result of the comparison of the facial image data.