For the purpose of protecting personal data, and to exclude systematic comparisons which should be forbidden, the processing of Eurodac data should only take place in specific cases and when it is necessary for the purpose of preventing, detecting or investigating terrorist offences or other serious criminal offences. A specific case exists, in particular, when the request for comparison is connected to a specific and concrete situation, to a specific and concrete danger associated with a terrorist offence or other serious criminal offence, or to specific persons in respect of whom there are serious grounds for believing that they will commit or have committed any such offence. A specific case also exists when the request for comparison is connected to a person who is the victim of a terrorist offence or other serious criminal offence. The Member States’ designated authorities and the Europol designated authority should thus only request a comparison with Eurodac when they have reasonable grounds to believe that such a comparison will provide information that will substantially assist them in preventing, detecting or investigating a terrorist offence or other serious criminal offence.