In attempting to determine whether a missing person has died there is a legal presumption that they are alive until proved dead. Where evidence indicates that the mising person was subject to a particular peril, they will be legally presumed dead; in MN this time period is 4 years (but this time period may be shortened such as in the case of an airplane crash, etc. when no body is found). That all havig been said, a court will not make the assumption that a missing person is dead unless it is reasonable to assume so, therefore a person will not be declared legally dead without proof that a genuine and complete search was made for them.