In Policy Patrol 8, subject codes are by default not case sensitive. If you want the subject codes to be case sensitive, set the system parameter 'MP_ACT_DISCLAIMER_SUBJECT_CODE_CASESENS' to 1.
In Policy Patrol 7, the subject codes entered in the 'Add disclaimer/signature dialog' are case sensitive. If you want the subject code not to be case sensitive, you can create a word/phrase filter and leave the case sensitive check box unchecked. Then select this word filter as a condition or exception in the rule (Subject contains word from filter).