Laws and court decisions make a distinction between "actual knowledge" and "constructive knowledge." "Actual knowledge" means a person "must have known" as opposed to "should have known." In footnote 4 of Uccello v. Laudenslayer (1975) 44 Cal App 3d 504, the court stated:
"[A] defendant's actual knowledge may be shown, not only by direct evidence, but also by circumstantial evidence. Hence, his denial of such knowledge will not, per se, prevent liability. (Cf. Fleharty v. Boltzen, 137 Cal. App.2d 187 [290 P.2d 311]; Desherow v. Rhodes, 1 Cal. App.3d 733, 747 [82 Cal. Rptr. 138]; 35 Cal.Jur.2d, Negligence, § 255, pp. 799-800.) However, actual knowledge can be inferred from the circumstances only if, in the light of the evidence, such inference is not based on speculation or conjecture. Only where the circumstances are such that the defendant 'must have known' and not 'should have known' will an inference of actual knowledge be permitted. (Cf. Young v. Carlson, 128 Cal. App.2d 743, 747-750 [276 P.2d 23].)"