Question: Can an expert and/or lay witness testify that another witness is or is not telling the truth during the course of a trial?
Answer: No, see below.
As a general rule, a party may not present an argument or issue on appeal unless that party raised that argument or issue before the trial court during the course of the trial. In such circumstances, the argument is deemed waived and will not be addressed by the appellate courts. Nonetheless, the Rule that relates to opinion evidence of truthfulness of another witness provides: “witnesses may not testify to opinions concerning intent, guilt, or innocence in a criminal case; the truth or falsity of allegations; whether a witness has testified truthfully; or legal conclusions.” Neither can lay witnesses, nor expert witnesses, competently testify that another witness is or is not telling the truth.” Thus, an attorney at trial may not ask a witness about another witness’ testimony by asking, “Do you believe that to be the truth?” Indiana Courts have repeatedly stated that such a question is highly improper. Again, neither lay witnesses nor expert witnesses are competent to testify that another witness is or is not telling the truth.