California Code, Government Code - GOV § 830.5

(a) Except where the doctrine of res ipsa loquitur is applicable, the happening of the accident which results in the injury is not in and of itself evidence that public property was in a dangerous condition.

(b) The fact that action was taken after an injury occurred to protect against a condition of public property is not evidence that the public property was in a dangerous condition at the time of the injury.