Section 13.15 Bias and Pecuniary Interest

• Library: Sources of Proof (2014 Ed.)

A. (§13.15) Bias and Pecuniary Interest

One of the most common forms of cross-examination is to show the pecuniary interest of the expert witness, thereby suggesting that financial interest motivates testimony in favor of the party paying the witness. See generally Michelle M. Ketchum, Experts: Witnesses for the Persecution? Establishing an Expert Witness’s Bias Through the Discovery and Admission of Financial Records, 63 UMKC L. REV. 133 (1994).

The courts have supported this technique, indicating that the jury is “entitled to know in whose interest the witness made the examination, and who paid him for his services, and everything which affected the credibility of the witness, and the weight to be given to his testimony.” Hall v. Fulton Iron Works Co., 31 S.W.2d 81, 83 (Mo. 1930). The pecuniary interest may be shown in a variety of ways, such as:

· showing that the expert receives 44% of the expert’s professional income from one law firm, State ex

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