Mich. Comp. Laws § 700.2501: Will; maker; sufficient mental capacity.

Sec. 2501.

(1) An individual 18 years of age or older who has sufficient mental capacity may make a will.

(2) An individual has sufficient mental capacity to make a will if all of the following requirements are met:

(a) The individual has the ability to understand that he or she is providing for the disposition of his or her property after death.

(b) The individual has the ability to know the nature and extent of his or her property.

(c) The individual knows the natural objects of his or her bounty.

(d) The individual has the ability to understand in a reasonable manner the general nature and effect of his or her act in signing the will.