From my adventures into mortgage banking and now compliance officer at a bank, performing CIP on a non-applicant spouse who signs the mortgage documents has always been conducted. The reasoning has been in that since the bank does not get to "meet" the non-applicant spouse through the underwriting process, when the mortgage is signed, the bank needs to identify and CIP verify that person. Risk? An "innocent" spouse may be the applicant and borrower, but a "nasty scammer" the non-applicant. Am I going overboard with the CIP?

ID'ing these parties is the prudent thing to do.