Comment

The Committee recommends the so-called synergistic effect instruction, which is included at the end of each of the relevant statutes units of the instructions in this chapter.

Use of a synergistic effect instruction was upheld against certain challenges in Gray v. State, 152 S.W.3d 125 (Tex. Crim. App. 2004). Judge Cochran, joined by Judge Meyers, dissented on the ground that the instruction “is not part of the law applicable to the case, and it is a comment on the weight of the evidence.” Gray, 152 S.W.3d at 138 (Cochran, J., dissenting). The majority characterized the contention that the instruction was a comment on the weight of the evidence as one presented by one of Gray’s grounds for review that was refused. “We do not address that claim today.” Gray, 152 S.W.3d at 134.

The Committee believed that the instruction is a part of the substantive definition of the statutory terms and thus should not, and ultimately will not, be regarded as a prohibited comment.

Gray was reaffirmed in Otto v. State, 273 S.W.3d 165, 170 (Tex. Crim. App. 2008). Otto held that when the state was limited to proving intoxication on alcohol, the jury instruction expanded beyond the charging instrument if it contained a concurrent causation instruction permitting conviction on proof that the defendant’s intoxication was caused concurrently by alcohol and another substance. The instruction recommended by the Committee contains no such concurrent causation provision.

The instruction does not require that the defendant be aware that the medication or other substance will interact with the alcohol and increase the alcohol’s intoxicating effects. Some members of the Committee believed that fairness requires that the synergistic effect analysis be used only if the evidence shows the defendant was aware that the other substance would have this impact.