The Texas Supreme Court has just muddied the waters of its causation jurisprudence. For the last twenty years the court moved in a straight line towards a modern theory of legal causation. The court recognized the problem of causality; put fault back at the heart of torts – even in product liability cases; reaffirmed the counterfactual account of causation holding that plaintiffs must prove that "but for" the defendant’s act or omission they’d be uninjured today; and, put reasonableness, and its best measure, the risk imposed, at the center of the calculus of how to define the limits of liability. Suddenly, everything (may have) changed.

In Transcontinental Insurance Company v. Crump, a worker’s compensation case, the court held that a jury must not only be queried as to whether a putative cause was a "but for" cause, they must also be asked whether the alleged cause was a "substantial factor". As the court recognized years ago, in the context of causation in tort there’s generally to be found the concept of substantiality "in which there always lurks the idea of responsibility.." Ok, but workers’ comp is a no-fault scheme. What is "substantial factor" doing in a comp case then?

Maybe, just maybe, the court has come to think of "a substantial factor" as being a "big cause" – this is the idea that one or more necessary causes are somehow (despite them each being necessary) more significant than other (logically equal) necessary causes. They could have adopted something like a proximate cause concept (the idea of circumscribing those causes upon which liability may be predicated) but didn’t – likely because the act itself uses the term "producing cause" long understood to mean a "but for" cause wherever it’s found along the causal chain. As a result they may well have stripped "the idea of responsibility" from Texas’ conception of "substantial factor".

If that’s the case it’s time for Texas’ mass tort plaintiff lawyers to shake off the blues. A substantial factor test shorn of concern about responsibility means that Borg-Warner’s test of reasonableness – risk, is now simply a test of whether or not the putative cause was a big one. And when it comes to, say, mesothelioma, what "bigger" cause is there than asbestos? There’s now a good argument to be made that Judge Davidson’s requirement that any putative cause be a sufficient cause in order to survive Borg-Warner sets the bar too high and that plaintiffs need only show that among all exposures adding up to .1 fiber/cc/yr the ones of which they complain are relatively "big". Good grief.