What is the authority for the rule on subsequent remediation evidence?

Governing California Authority

In a California state-court action, the controlling authority is Evidence Code section 1151. It bars evidence of subsequent remedial or precautionary measures when offered to prove negligence or culpable conduct.

“When, after the occurrence of an event, remedial or precautionary measures are taken, which, if taken previously, would have tended to make the event less likely to occur, evidence of such subsequent measures is inadmissible to prove negligence or culpable conduct in connection with the event.”[3]

The California Supreme Court has explained that the statute excludes such evidence only when offered to prove negligence or culpable conduct, and does not bar evidence offered for a relevant, non-negligence purpose.[4] For example, subsequent repairs may be admissible to show disputed control of the property, subject to appropriate limitations.[2]

Application and Limits

The rule applies to evidence of measures taken after the event that, had they been taken beforehand, would have tended to make the event less likely. It is not a blanket bar to all evidence concerning what happened afterward. The proponent may argue that the evidence is offered for another relevant purpose; the opposing party may seek an admission or other limitation to remove the disputed issue supporting that purpose.[2]

One important qualification: Ault held section 1151 does not exclude subsequent design changes when offered in a strict-products-liability action, because that claim does not require proof of negligence or culpable conduct.[4]

Federal Court

If the case is in federal court, the parallel provision is Federal Rule of Evidence 407, which also bars subsequent measures as proof of negligence or culpable conduct, while allowing possible admission for specified other purposes, including disputed ownership, control, or feasibility.[1]