Deceased clients can do all sorts of things that they shouldn't, like:
be booked in, or remain booked in, to shelter
have open case files
have open housing placements or housing loss prevention records
have open subsidies
really, have open anythings
My suggestion is when you make a client Deceased, have a little procedure that occurs, with a popup for the user that says "the following records will be closed:" and then list everything that's open for the client and close them all. When there is a reason required, like reason for discharge, then the reason should automatically be deceased. Then have an "okay to proceed" button.
As of 4.0.60.5.1, marking a client as Deceased also expires their Consent record.