Plaintiffs brought this products liability action against defendant, Square D Company, following the death of plaintiffs’ decedent, Chester W. Skinner. Mr. Skinner was electrocuted by his own homemade tumbling machine on which he had installed a switch manufactured by defendant. Plaintiffs appeal as of right a circuit court order entering summary disposition in favor of defendant pursuant to MCR 2.116(0(10). We affirm.
i
This is a tragic case. Plaintiffs’ decedent was in the business of cleaning and finishing metal parts. To this end, Mr. Skinner routinely used a homemade tumbling machine that he had designed and *666built himself. Essentially, the machine consisted of a large metal drum mounted on a frame. Rough metal parts were placed inside the drum along with a quantity of abrasive detergent. An electric motor then rotated the drum in one direction to wash the parts. After allowing the drum to rotate for a period of time, the operator would reverse the direction of the tumbler and the finished parts would be ejected from the drum.
Because of the way Mr. Skinner had designed the machine, reversing the direction of the drum’s rotation was a dangerous task. The motor that turned the drum was controlled by a switch manufactured by defendant. Mr. Skinner had connected the Square D switch to the motor by using three wires with insulated "alligator clips” on the ends. In order to reverse the direction of the machine, the operator was required to disconnect two of the alligator clips from the motor by hand and reverse them. For obvious reasons, it was important for the operator to make sure that the Square D switch was in the off position before disconnecting the wires from the motor.
On February 21, 1986, Mr. Skinner was in his shop, working in the room with the tumbling machines. Mrs. Skinner and two other women, Beulah McBride and Violet Whiting, were in another room, racking parts. Suddenly, the women heard Mr. Skinner cry out. They ran into the room where Mr. Skinner was, and found him standing with his hands above his head, each hand grasping an alligator clip. Electric current was passing through Mr. Skinner’s body. Aware of what was happening, Mr. Skinner cried out to the women,' "don’t touch me”! He then freed his left hand from the alligator clip and reached for the Square D switch. Mr. Skinner threw the switch into the off position, twisted, and fell over dead.
*667II
It is plaintiffs’ theory in this case that a defect in the design of the Square D switch proximately caused Mr. Skinner’s electrocution. Plaintiffs allege that the switch was defective because it had a large "dead zone” that allowed the switch to be positioned in such a way that it would appear to the operator to be off when it was actually on.
Defendant argues, and the trial court agreed, that even assuming the switch was defective, there is no evidence that Mr. Skinner was actually confused or misled by the position of the switch at the time he was electrocuted. Thus, defendant submits, no genuine issue of material fact exists concerning whether the alleged defect proximately caused Mr. Skinner’s death. After a thorough review, we are constrained to agree with defendant’s argument.
It is well established in Michigan law that a prima facie case for products liability requires proof of a causal relationship between the defect and the damage of which the plaintiffs complain. Mulholland v DEC Int'l Corp, 432 Mich 395, 415; 443 NW2d 340 (1989). It is also true that a prima facie case does not require that a plaintiff offer evidence that positively excludes every other possible cause. Rather, it is enough if the plaintiff can establish a logical sequence of cause and effect, notwithstanding the existence of other plausible theories, although other plausible theories may also have evidentiary support. Id.
The element of causation, however, cannot be established solely on the basis of theory or conjecture. Jordan v Whiting Corp, 396 Mich 145, 151; 240 NW2d 468 (1976). It is the plaintiff who bears the burden of proving causation, and where the matter is one of pure speculation or conjecture, it *668becomes the duty of the trial court to direct a verdict for the defendant. See Mulholland, supra at 416-417, n 18, quoting Prosser & Keeton, Torts (5th ed), § 41, p 269. Similarly, mere conjecture does not meet the burden of proof imposed on a party opposing a motion for summary disposition to come forward with documentary evidence indicating that a genuine issue of material fact exists. Little v Howard Johnson Co, 183 Mich App 675, 683; 455 NW2d 390 (1990).
Applying these principles to this case, we are persuaded that the trial court did not err in granting defendant’s motion for summary disposition. Throughout this litigation, both sides have advanced various theories regarding how the accident occurred. However, at no time did plaintiffs advance a plausible theory regarding how the defective switch caused the accident. We agree with the following observations contained in defendant’s brief:
Throughout the course of this litigation, plaintiffs have failed to appreciate that their burden is not simply to produce evidence that the switch could possibly, theoretically be confusing to someone at some time. They must produce evidence from which a jury could reasonably conclude that Mr. Skinner was in fact confused by the Square D switch on the machine he was operating just before he was electrocuted and that this confusion led to his death. See . . . Derbeck v Ward, 178 Mich App 38, 44 [443 NW2d 812] (1989); and Jubenville v West End Cartage, Inc, 163 Mich App 199 [413 NW2d 705] (1987).
The absurdity of plaintiffs’ confusion theory is exposed as soon as one realizes that the operator of the tumbling machine did not depend upon the way the switch handle appeared to determine whether the machine was "on” or "off.” Even if Mr. Skinner pushed the handle of the switch *669incompletely or even if it somehow teased its way into an ambiguous position, Mr. Skinner could not have thought the machine was off if in fact it was still running! The noise of the tumbler barrel and the motor is deafening and the motion of the barrel is continuous. Thus, even if Mr. Skinner were careful and tried to turn the machine, off before unfastening and refastening the alligator clips, he would have had to have known that the switch had not turned the power off because the machine would still have been running. He could not have ignored the roar of the motor and overlooked the tumbler as it turned continuously directly in front of him! [Emphasis in original.]
The scenarios advanced by plaintiffs in an attempt to establish causation are well characterized by defendant as "Agatha Christie theories.” We acknowledge that proximate cause is usually a question of fact and that summary disposition is appropriate only in exceptional cases. See Derbeck v Ward, supra. In this case, we have carefully reviewed all plaintiffs’ scenarios and find none to be supported by fact or reason. Without a plausible theory of causation, plaintiffs’ claim must fail and summary disposition is warranted. For this reason, we conclude that the trial court did not err in granting defendant’s motion for summary disposition.
m
We turn now to plaintiffs’ remaining arguments on appeal. Plaintiffs next contend that the trial court erred in granting defendant summary disposition without ruling specifically on plaintiffs’ separate claims of failure to insulate and failure to warn. We disagree.
Plaintiffs argue that the Square D switch was defective because it was not made of insulated *670material and that there is evidence that this defect contributed to Mr. Skinner’s electrocution. We find this argument disingenuous and accordingly reject it. It does appear that the experts agree that when Mr. Skinner grabbed the switch, he provided a secondary ground for the current that increased the magnitude of the shock he received. The testimony relied on by plaintiffs, however, does not indicate that it was only at that instant that the shock became fatal. Contrary to plaintiffs’ assertion, Dr. Klingler, a witness for the plaintiffs, did not conclude that it was the act of shutting the power off that caused Mr. Skinner’s death:
Q. [attorney for the defendant]: Is it your opinion that if the operating mechanism on this switch had been insulated, that Mr. Skinner would not have been electrocuted?
A. [Dr. Klingler]: I just don’t know. He may have received an extreme shock. He may still have been electrocuted.
I don’t know. I can’t say about that.
Dr. Klingler also admitted that his testimony was speculative. When asked if Mr. Skinner could have been electrocuted before he had a chance to reach for the switch, Klingler replied, "Oh, sure.” Similarly, the pathologist who conducted an autopsy, Dr. Kallet, testified that Mr. Skinner had already completed the circuit by the time he grabbed for the switch, with the current entering his right hand and exiting through the balls of his feet. We find no basis for relief on this issue.
Finally, plaintiffs contend that a question of fact exists regarding whether defendant was negligent in failing to place a warning label on the defective switch box. Our finding that plaintiffs have not shown that the defect was a proximate cause of the accident renders this issue moot.
*671Affirmed.
Jansen, P.J., concurred.