Ex-Post Right, Ex-Ante Wrong

28 Pages Posted: 9 Nov 2012 Last revised: 12 Mar 2014

See all articles by Ariel Porat

Ariel Porat

Tel Aviv University; University of Chicago - Law School

Date Written: September 30, 2012


Should a doctor be held liable under negligence law for harmful treatment she administered to a patient, if the treatment should have been considered negligent at the time it was administered, but is now considered reasonable at the time of trial? Should a manufacturer be held liable for harm caused to a consumer from a product considered reasonable, and therefore non-defective, at the time of trial, but should have been considered unreasonable, and therefore defective, at the time of its distribution? More generally put: Should the law impose liability for ex-post right but ex-ante wrong behaviors? The answer offered by this Article is yes, on both efficiency and corrective justice grounds. The Article also proposes the adoption, in certain cases, of an “Alternative Liability Rule,” whereby an injurer bears liability if his behavior is either ex-post or ex-ante wrong.

Thus far, there are no reported cases where a plaintiff brought suit for ex-post reasonable but ex-ante unreasonable behavior or products. This is puzzling, especially given the abundance of reverse cases before the courts, where the defendant’s behavior or product is found to be ex-post unreasonable but ex-ante reasonable, and liability is not imposed. The Article’s explanation for the lack of suits for ex-post right but ex-ante wrong behavior is plaintiffs’ and their attorneys’ strong belief that when a behavior, or a product, is considered reasonable at the time of trial, it is considered reasonable by the law. The claim made in the Article is that this belief is unfounded and a plaintiff who proves ex-ante negligence should succeed at trial, regardless of whether the defendant’s behavior is considered reasonable at that time.

Keywords: Negligence, products liability, medical malpractice, ex ante and ex post negligence, design defect, state of the art defense, silicone breast implants litigation

Suggested Citation

Porat, Ariel, Ex-Post Right, Ex-Ante Wrong (September 30, 2012). Notre Dame Law Review, Vol. 89, 2014, University of Chicago Institute for Law & Economics Olin Research Paper No. 617, Available at SSRN: https://ssrn.com/abstract=2172932 or http://dx.doi.org/10.2139/ssrn.2172932

Ariel Porat (Contact Author)

Tel Aviv University ( email )

Ramat Aviv
Tel Aviv, 69978
972-3-6408283 (Phone)
972-3-6407260 (Fax)

HOME PAGE: http://english.tau.ac.il/profile/porata

University of Chicago - Law School ( email )

1111 E. 60th St.
Chicago, IL 60637
United States

HOME PAGE: http://www.law.uchicago.edu/faculty/porat

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