Mobile terminal for capturing biometric data of a user, comprising: - a data memory which contains a credential that is specifically assigned to the user, the credential identifying the mobile terminal as being authorized, the data memory being configured for capturing and storing the biometric data of the user, the data memory containing a specification of a permissible time period; - an authentication module configured for authenticating the user to the mobile terminal by means of authentication data assigned to the user and for authenticating the mobile terminal to the user by means of the stored credential; - a sensor (208, 210) configured for capturing the biometric data of the user; - a clock configured for capturing a current time while the biometric data are being captured; - a control unit configured for capturing the biometric data of the user automatically or semi-automatically by means of the sensor only upon successful mutual authentication of the user and the mobile terminal; - a checking unit configured for automatically checking the authenticity of the captured biometric data; - wherein the control unit is configured for storing the captured biometric data in the data memory in protected form only when the captured biometric data are authentic according to the check, the captured biometric data only being stored in the mobile terminal when the current time captured while the biometric data are being captured is within the permissible time period; - wherein the authentication module is configured for authenticating an operator to the mobile terminal by means of additional authentication data assigned to the operator; - wherein the control unit is configured for allowing the biometric data stored in a protected manner to be read out only in the event of successful authentication of the operator, in order to transmit the read-out biometric data to a security document. - a data memory which contains a credential that is specifically assigned to the user, the credential identifying the mobile terminal as being authorized, the data memory being configured for capturing and storing the biometric data of the user, the data memory containing a specification of a permissible time period; - an authentication module configured for authenticating the user to the mobile terminal by means of authentication data assigned to the user and for authenticating the mobile terminal to the user by means of the stored credential; - a sensor (208, 210) configured for capturing the biometric data of the user; - a clock configured for capturing a current time while the biometric data are being captured; - a control unit configured for capturing the biometric data of the user automatically or semi-automatically by means of the sensor only upon successful mutual authentication of the user and the mobile terminal; - a checking unit configured for automatically checking the authenticity of the captured biometric data; - wherein the control unit is configured for storing the captured biometric data in the data memory in protected form only when the captured biometric data are authentic according to the check, the captured biometric data only being stored in the mobile terminal when the current time captured while the biometric data are being captured is within the permissible time period; - wherein the authentication module is configured for authenticating an operator to the mobile terminal by means of additional authentication data assigned to the operator; - wherein the control unit is configured for allowing the biometric data stored in a protected manner to be read out only in the event of successful authentication of the operator, in order to transmit the read-out biometric data to a security document.