Indiana Code Title 36. Local Government § 36-9-25-22

Sec. 22. (a) If a person having an interest in land affected by the proceedings is mentally incompetent or under eighteen (18) years of age, the board shall certify that fact to its attorney.

(b) The attorney shall apply to the proper court and secure the appointment of a guardian for that person.  The board shall then give notice to the guardian, who shall appear and protect the interest of the protected person.  However, if the mentally incompetent person or person under eighteen (18) years of age already has a guardian, the notice may be served upon that guardian.  The requisites of notice to the guardian are the same as for other notices.

(c) If there are defects or irregularities in the proceedings with respect to one (1) or more interested persons, they do not affect the proceedings unless they touch the interests or property of the person or persons and do not affect any other person.  If a defect does exist, supplementary proceedings may be had in order to supply them.