Preponderance of the Evidence – Washington Pattern Instruction 21.01

Posted Tuesday, July 25, 2017 by Ed Harper

“When it is said that a party has the burden of proof on any proposition, for that any proposition must be proved by a preponderance of the evidence, for the expression ‘if you find’ is used, it means you must be persuaded, considering all the evidence in the case bearing on the question, that the proposition on which the party has the burden of proof is more probably true than not sure.” This instruction is based on the case Cox v. Spangler, (cite omitted). This burden of proof falls on the plaintiff, regarding the injuries which allegedly have been caused by the defendants.

To establish a causal connection in most civil matters, the standard of confidence required is a “preponderance,” or more likely than not, more than 50%. According to Lloyd L, Wiehl, “In essence the Washington court has reduced the burden to the probability factor.” (Lloyd L. Wiehl, Our Burden of Burdens, 41 Wash. L. Rev. 109, 110)

The case of Anderson v. Akso Noble Coatings, Inc. 172 Wn. 2nd 593, 260 P 3rd 857, (2011), sheds light on this issue regarding an attempt by the defendants to establish medical issues with a potentially higher standard “a reasonable degree of medical certainty”. The plaintiff must establish their damages beyond the realm of speculation. The medical testimony must at least be sufficiently definite to establish that the act complained of “probably” or “more likely than not” caused the later disability.

The defendants if attempting to prove a different event caused injuries or damages, the burden falls on them to establish this other event caused injury. In Anderson, Justice Chambers establishes “expert medical testimony must meet the standard of reasonable medical certainty or reasonable medical probability” (Anderson at 606 – 607)

Justice Chambers notes that reasonable medical probability and reasonable medical certainty are used interchangeably.

In Anderson, Julie Anderson sued her employer for injuries caused to her unborn child while she worked at the paint company, Akso Nobel Coatings. One medical expert concluded Anderson’s young infant’s developmental malformations were likely due to his mother’s paint exposure at Akso. The doctor referring to the young child’s issues stated “significant medical problems very likely a result of significant exposure to organic solvents used in utero.” Additionally, plaintiff Anderson relied heavily upon the expert opinion of one of her doctors, who was prepared to testify “within a reasonable degree of medical certainty, as to the cause of her young son’s malformations as being in utero workplace exposure to her while employed at Akso Nobel. (Anderson at 603 – 604)

The defendants argued that under the Frye standard the theory of causation mentioned above must be “generally accepted” in the scientific community. The trial court agreed that under Washington common law there must be consensus of scientific opinion on the issue of specific causation and granted the motion in limine excluding Anderson’s expert’s testimony. The Supreme Court disagreed via Justice Chambers opinion as stated above. (Anderson at 612)

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