In the case of Johnson v. Watkins, 70 Nev. 156, 262 P.2d 237 (1953) a truck driver tried to invoke the rule regarding evidentiary inferences in his favor. According the Nevada Supreme Court an evidentiary inference is:
a logical and reasonable conclusion of a fact not presented by direct evidence but which, by process of logic and reason, a trier of fact may conclude exists from the established facts. Although an inference may give rise to a rebuttable presumption in appropriate cases, an inference simply allows the trier of fact to determine, based on other evidence, that a fact exists. An inference is permissible, not required, and it does not shift the burden of proof. Bass-Davis v. Davis, 122 Nev. 442, 134 P.3d 103 (2006)
The Johnson case gives a great example of an inference and how inferences are invoked. In Johnson, the truck driver was hurt in an accident immediately after he had helped unload his trailer. He attached a pulley and tackle to the logs on his truck and a caterpillar tractor lifted the load off the truck. Afterward, the driver climbed down off the bed of the truck and secured the pulley to the pole that held the pulley up. He got back up on the bed truck and started to secure his equipment when the pulley swung free and hit him in the head.
Plaintiff argued to the court that the caterpillar driver must have pulled the cable higher on the pole, causing it to swing free and hit him. Plaintiff asked the court for an inference based on the law of physics. He said that when he secured the pulley to the pole, he tied it off at about 5 feet up. He testified that when he was hit he was standing on the bed of his truck which would have put his head at about 9 feet up. He concluded that a pendulum inadvertently released at 5 feet could not reach him that height and that the caterpillar must have pulled it up there.
However, the caterpillar driver said he didn’t move the Cat and that rather than standing, the driver was crouching on the truck bed when he was hit.
Ultimately, the court determined that Plaintiff couldn’t rely on an inference when the facts did not support such an inference.
The lesson learned for this truck driver, and for all who rely on this case, is that inferences are permissive and if the evidence supporting the inference is tenuous or disputed, the court may not permit such an inference to be used by the jury.