There was no error in admitting evidence of the defendant's prior convictions for impeachment purposes. Commonwealth v. Leno, 374 Mass. 716 , 717-718 (1978). It was within the judge's discretion to instruct the jury as to the limited purpose for which the records of conviction were offered at the time they were introduced or, as he did, in his charge. Commonwealth v. Ferguson, 365 Mass. 1 , 11 (1974). There is no merit to the defendant's assertion (which does not rise to the level of appellate argument, Lolos v. Berlin, 338 Mass. 10 , 14 ) that there was error in the judge's limiting instruction as given.
1. The defendant claims that the judge erred in failing sua sponte (see Commonwealth v. Harris, 371 Mass. 462 , 470-471 ) to instruct the jury to consider the voluntariness of an admission. After a voir dire hearing the judge had made an initial determination that the admission was made voluntarily and would be admissible in evidence. We need not concern ourselves with whether the "humane practice" applies to admissions as well as confessions (see Commonwealth v. Garcia. 379 Mass. 422 , 432-434 ; see Commonwealth v. Vick, 381 Mass. 43 , 45-46 ) because there was no evidence before the jury from which it could have been inferred that the admission was not voluntary. It was thus not a live issue at trial, and the judge was not required to instruct the jury on his own that, if they should find the admission to have been involuntarily made, they should disregard it. Commonwealth v. Alicea, 376 Mass. 506 , 522-523 (1978). Commonwealth v. Cole, 380 Mass. 30 , 40-41 (1980). Commonwealth v. Roberts, 6 Mass. App. Ct. 891 (1978).
2. The defendant's claim that the judge erred in failing to strike a comment made by the prosecuting attorney in his closing argument "attacking
the integrity of defense counsel's examination of a defense witness" is without merit. The questioned comment was directed to the truthfulness of the witness, not the integrity of counsel. See Commonwealth v. Fitzgerald, 376 Mass. 402 , 422 (1978).