Sec. 10. (a) In all cases in which:
(1) executors, administrators, heirs, or devisees are parties; and
(2) one (1) of the parties to the suit is incompetent under this chapter to testify against the parties described in subdivision (1);
the assignor or grantor of a party making the assignment or grant voluntarily shall be considered a party adverse to the executor or administrator, heir, or devisee.
(b) However, in all cases referred to in sections 4 through 9 of this chapter, any party to the suit has the right to call and examine any adverse party as a witness.
(c) The court may require any party to a suit or other person to testify. Any abuse of the court's discretion under this subsection is reviewable on appeal.