The defendant appeals from his convictions of assault with intent to rape, assault and battery by means of *258 a dangerous weapon, and breaking and entering with intent to commit a felony (rape). There was evidence to the effect that he had been identified from a photographic array by the victim as the person who, some time between three-thirty and four o’clock the morning of April 10, 1982, entered her home, awoke her, directed her to “[t]ake off your clothes, you whore,” and, upon her refusal, beat her around the chest and face with his fists. The assailant’s left hand had a ring, described as large, which may have been responsible for breaking one tooth, chipping another, and gashing her forehead. He abruptly stopped the attack, put on dark glasses and fled. The victim had not seen her assailant previously but later that day selected his photo from the array (which is before us), apparently without hesitation.
The defendant gave detailed, somewhat unusual, alibi testimony which was corroborated by three witnesses, and he introduced as well evidence that he had passed a lie detector test. Before the defendant testified, his counsel pressed a motion addressed to the judge’s discretion under
Commonwealth
v.
Chase,
At no time was it brought to the judge’s attention that the three assault and battery convictions were not admissible for impeachment purposes under the terms of G. L. c. 233, § 21. In none had a sentence been imposed. One had been placed on file; on the others the defendant had been placed on proba
*259
tian. Unlike a felony, as to which by the express terms of § 21, a plea, verdict, or finding of guilt suffices for admissibility regardless whether sentence is imposed, a misdemeanor is inadmissible unless a sentence has been imposed. See
Forcier
v.
Hopkins,
The defendant argues on appeal that his conviction should be reversed for ineffective assistance of counsel. Other than permitting the three assault and battery convictions to go to the jury, trial counsel handled the defense with a high degree of professional competence.
2
Still, the admission of the convictions cannot reasonably be thought to be other than a lapse by defense counsel. The Commonwealth’s case turned entirely on identification evidence, the potential for unreliability of which is well recognized;
3
there was no (or virtually no
4
) cor
*260
roboration. The defendant’s alibi was plausible and well supported. He had submitted to, and passed, the lie detector test. But for learning of the three prior convictions of forcible acts against women, the jury could well have reached the conclusion that the victim’s identification was mistaken. For the unusual dangers of prejudice inherent in the admission of prior convictions of crimes similar in nature to those charged, see
Commonwealth
v.
DiMarzo,
Despite the over-all quality of the defense, a mistake as serious in its likely effect as this amounts to ineffective assistance of counsel, whether it is regarded as simple oversight or as a tactical judgment that was “manifestly unreasonable.”
Commonwealth v. Adams,
*261
The defendant’s other contentions are unavailing. The reliability of the identification was a question of fact for the jury.
Commonwealth
v.
Fitzgerald,
The judgments are reversed, the verdicts are set aside, and the cases are remanded for further proceedings consistent herewith.
So ordered.
Notes
See
Commonwealth
v.
Cadwell,
The defendant suggests that his trial counsel displayed ineffectiveness in failing to obtain a blood test of stains on the victim’s sweatshirt. The prosecutor argued to the jury that the stains were probably caused by the defendant’s bleeding (see note 4, infra); but a test conducted after trial, in connection with the defendant’s motion for a new trial, disclosed that the stains were not of the defendant’s blood but could have been of the victim’s blood. The judge properly concluded that the point was not of such probative significance as to warrant a new trial; and defense counsel may have been reluctant before trial to obtain a test, the results of which (if adverse) could tend to incriminate the defendant even if he had been wrongly identified as the intruder.
Simmons
v.
United States,
The victim had stated to the police that, in the course of fighting off her attacker, she had scratched the left side of his face. When arrested later the day of the crime, the defendant had a not particularly remarkable cut on the center of his lower lip. (The cut appears in a photograph in evi *260 dence.) The hospital report shows that the victim told hospital personnel that her attacker cut his hand and was bleeding when he left, leaving a trail of blood. When the defendant was arrested, his hands were not cut, although an officer testified that the knuckles appeared to have been bruised. The net corroborative value of this testimony could variously be regarded as slight, nonexistent, or even negative. The defendant wore a large ring on his left hand, but so do many men. The ring was not tested for traces of the victim’s skin, blood, or hair.
The Commonwealth concedes that the assault and battery convictions were inadmissible but argues that no harm was done. The first reason ad
*261
vanced is that the prior burglary conviction, which was admissible, was more serious, being a felony, than the three misdemeanor convictions. That type of argument is often sound, see
Gilday
v.
Commonwealth,
