That is, unfortunately, a result of an inappropriate table schema. You'll want to fix that rather than create a work-around.
You need a "Subject" table with this information ONLY: Firstname, LastName, address, city, and state.
You also need a "Case" table with the case information ONLY.
To link, or relate, the two tables, you need to apply relational database concepts.
The Subject table needs a Primary Key (we usually use the AutoNumber for this). Make sure you designate it as the PK.
The Case table needs its own Primary Key (again, usually the AutoNumber). It will also have a Foreign Key field. In the Foreign Key field, insert the appropriate PK for the subject. NO need to duplicate the demographic subject into again and again and again.... The PK-->FK relationship identifies that for you.
Data entry is done through a main form/sub form design.
The main form is bound to the Subject table. The sub form is bound to the Case table. There is a property for the subform control to Link Master and Child Fields to synchronize them and insert the proper PK values into the Case table records. Use SubjectID for this.
No more duplication.