¶1(dissenting). I respectfully dissent. Today we decide that an otherwise competent defendant is rendered incompetent by virtue of a delusion based mental illness that we presume gives rise to a defense of lack of criminal responsibility and simultaneously prevents him from recognizing and therefore assisting in the presentation of that defense. We do so without ever having heard from the parties as to the correctness or wisdom of such a far-reaching precedent.
¶2The judgment should be affirmed for the reasons set forth in the Appendix to the majority opinion. Since the defendant never raised the issue of his competence either at trial or on appeal, it is not for us to act on his behalf. Mass.R.A.P. 16(a)(4), as amended, 367 Mass. 921 (1975). Commonwealth v. Vincente, 405 Mass. 278 (1989). Commonwealth v. Hampton, 26 Mass. App. Ct. 938 (1988). Neither the experienced trial judge, *167stand-by defense counsel, nor the prosecutor ever expressed any concern about the defendant’s competence during trial.
¶3If the defendant decides to pursue the issue of his competence to stand trial, the open course is to move for a new trial pursuant to Mass.R.Crim.P. 30(b), 378 Mass. 900 (1979). See Commonwealth v. Hill, 375 Mass. 50, 52 (1978).