In conversion, an array of defenses are available to the defendant such as:

• Abandonment
• Authority of law
• Consent or approval
• Statutes of limitations
• Interest of defendant
• Lack of value of property
• Nonexistence or lack of identity of property
• Privilege
• Unlawful and illegal acts
• Waiver, ratification, and estoppel.

Some rejected defenses include contributory negligence, assumption of risk, mistake, good faith, due care, equitable defenses of estoppel, unclean hands, complete innocence, and perfect good faith[i].

[i] In re Davis, 172 B.R. 437 (Bankr. D. D.C. 1994); Ligon v. E. F. Hutton & Co., 428 S.W.2d 434 (Tex. Civ. App. Dallas 1968); U.S. v. North Side Deposit Bank, 569 F. Supp. 948 (D. Pa. 1983);  Taylor v. Forte Hotels International, 235 Cal. App. 3d 1119, 1 Cal. Rptr. 2d 189 (4th Dist. 1991);  Warren v. Warren, 784 S.W.2d 247 (Mo. Ct. App. W.D. 1989);  American Petrofina, Inc. v. PPG Industries, Inc., 679 S.W.2d 740, 40 U.C.C. Rep. Serv. 816 (Tex. App. Fort Worth 1984).