A witness will not be allowed to testify whether a person was under the "undue influence" of another, since this is considered a conclusion of law.  See also OPINIONS.

1.  Presumption

Undue influence will be presumed under certain circumstances, such as where the attorney  who prepared a client’s will is named as a beneficiary,{footnote}Franciscan Sisters Health Care Corp. v. Dean, 95 Ill. 2d 452, 448 N.E.2d 872 (1983).{/footnote} or where a person with fiduciary duties to the grantor is named as as grantee of a deed.{footnote}Lamb v. Lamb, 124 Ill. App. 3d 687, 464 N.E.2d 873 (1984)(must be rebutted by clear and convincing evidence).{/footnote}