How do I locate a deceased person if the case may be of unknown origin as to whether this person has a policy that is unknown to his survivors.

What relation are you to the deceased? The Executor to the estate has access to all of their records.

You look though all of their records, check bank payments to insurance companies,
You look for bills or statements in the mail for the next year or two.

The NAIC -National Association of Insurance Commissioners, the state officials who regulate the insurance industry- has a page on how to do this: Consumer Alert: Finding A Lost Insurance Policy