This is a will that is handwritten by the testator (the person creating the will) and is not witnessed. Michigan is one of several states that recognizes and accepts holographic wills. For a holographic will to be recognized it must meet the following requirements;

The holographic will must be dated
The testator must sign the will
The will must be in the testator’s handwriting
The will addresses issues of guardianship, personal representatives
and property distribution
It must be evident that the document was intended to serve as the
testator’s will.

A court will look at other documentation, some that is not handwritten by the testator to determine the validity of the will.

Forgery, contesting content and previously written wills make holographic wills ripe for contention.  Due to the potential for uncertainty, one should be very careful in relying on a holographic will.