A statement in a judicial opinion that isn't necessary to the holding is called a dictum (pl. dicta), and isn't technically binding (though it may or may not be persuasive). Here's a good example of that from a 1976 federal case (thanks, Daniel).
In Searight v. New Jersey, the plaintiff alleged that in 1962 the state had "unlawfully injected him in the left eye with a radium electric beam" and that since then someone had been talking to him "on the inside of his brain." Because he did not sue until 1976, the statute of limitations had long since run, and that was the basis of the state's motion to dismiss. The court noted that, although it would normally have given the plaintiff a chance to amend, here it wouldn't because it also lacked jurisdiction. Then it went on (and this is the dicta part):
The allegations, of course, are of facts which, if they exist, are not yet known to man. Just as Mr. Houdini has so far failed to establish communication from the spirit world …, so the decades of scientific experiments and statistical analysis have failed to establish the existence of "extrasensory perception" (ESP). But, taking the facts as pleaded, and assuming them to be true, they show a case of presumably unlicensed radio communication, a matter which comes within the sole jurisdiction of the [FCC]. And even aside from that, Searight could have blocked the broadcast to the antenna in his brain simply by grounding it. See, for example, Ghirardi, "Modern Radio Servicing", First Edition, p. 572, ff. (Radio & Technical Publishing Co., New York, 1935). Just as delivery trucks for oil and gasoline are "grounded" against the accumulation of charges of static electricity, so on the same principle Searight might have pinned to the back of a trouser leg a short chain of paper clips so that the end would touch the ground and prevent anyone from talking to him inside his brain.
But these interesting aspects need not be decided here.
Therefore, you could cite this case as precedent on limitations or federal jurisdiction, but not for the proposition that a plaintiff has a duty to ground himself. Personally I think the proposition is valid, I'm just saying you need to find another case.