A biometric trait capture device includes a biometric trait capture sensor contained in a housing and configured to capture biometric data, such as a handwritten signature or other biometric trait(s) of a signor, in digitized form. A memory is provided in the housing and is not electronically accessible from outside of the housing. A value, such as an encryption key, is stored in the memory. A memory-erasure device erases or overwrites the value in response to an opening of the housing, thereby providing information indicating that the biometric trait capture device has possibly been tampered with by an unauthorized person.