13-1424. Causation; independent intervening cause.

            The cause of an injury is that which, in a natural and continuous sequence [unbroken by any independent intervening cause], contributes to bringing about the injury and without which the injury would not have occurred. [It need not be the only cause, nor the last nor nearest cause. It is sufficient if it occurs with some other cause, acting at the same time, which, in combination with it, causes the injury.]

            ["Independent intervening cause" is that which interrupts the natural sequence of events which could reasonably be expected to result from the condition in which a product was sold or from a foreseeable manner of use. An independent intervening cause unforeseeably turns aside the course of events and produces a result which could not reasonably have been expected.]

                                                  DIRECTIONS FOR USE

            The phrase in the first brackets and the bracketed second paragraph will be used only if there is sufficient evidence of an independent intervening cause.

            The phrase in the last brackets of the first paragraph should be used only when there is evidence of a concurring or contributing cause.

            The applicable portions of this instruction must be used in all products liability cases. In an appropriate case, this instruction will be followed by UJI 13-1425 or 13-1426 NMRA, or both.

                                               COMMITTEE COMMENT

            With the exception of cause in warning cases, treated separately under UJI 13-1425 NMRA, the general tort law definition of causation is applicable in products liability cases. The first paragraph of this instruction is UJI 13-308 NMRA and the comment to that instruction is applicable.

            "Independent intervening cause" is one application of the principles of proximate cause. Kelly v. Montoya, 81 N.M. 591, 594-6, 470 P.2d 563, 566-8 (Ct. App. 1970); Baker v. Fryar, 77 N.M. 257, 260-2, 421 P.2d 784, 786-8 (1966); Thompson v. Anderman, 59 N.M. 400, 411-2, 285 P.2d 507, 514 (1955). While "independent intervening cause" is an argument generally raised by the defense, it is not an affirmative defense and it should be given as a companion instruction to proximate cause. The committee has, therefore, included "independent intervening cause" as a separate bracketed paragraph to the basic definition. In products cases, the issue frequently involves a defense contention that the conduct of the original purchaser (i.e., a parent, employer, etc.) was a major contributing factor to the accident and interrupted the natural sequence of events flowing from defendant's conduct. In cases of injury to bystanders, the contention may center upon conduct of the product's user. Also, the issue may arise in connection with UJI 13-1422 and 13-1423 and evidence that modifications or alterations in the product have materially changed the nature and magnitude of the risk of injury presented by the product's original condition or design.

            Court and counsel may feel that a party's argument on "independent intervening cause" should be spelled out in the instructions and not left solely to verbal explanation by the attorneys. A party's theory of "independent intervening cause" can be inserted in UJI 13-1401, though it should not be identified as a "defense" which must be proved by defendant.