In Robbins v. State, 717 S.W.2d 348 (Tex. Crim. App. 1986), an involuntary-manslaughter case that did not involve party liability, concurrent causation was not an issue and should not have been submitted to the jury; nonetheless, the trial court gave an erroneous causation instruction that it applied to the facts. Id. at 351. That instruction allowed conviction if the defendant's intoxication caused "or contributed to cause" the collision and death, without also providing any restriction on the degree of contribution, as required by section 6.04(a). Id. at 351-52. The court held that the erroneous instruction improperly lessened the State's burden of proof. Id. at 352.