In the case of a joint account the funds become the property of the survivor.
On presentation of the Death Certificate the deceased should then be removed from the account and the account may convert to a sole account.
This is the normal procedure AFAIK with all normal current a/c's and savings a/c's.
There are some cases where couples use just one ATM card on an a/c. It shouldn't really happen but sometimes they like to save the govt tax on cards. In the case you mentioned the card may have been in the husbands name, in which case it would have been cancelled to comply with procedure. Sometimes also the a/c is a sole a/c but a form has been signed to give another party signing authority. This would not give the other person entitlement to the funds on the death of the a/c holder.