A jury returned a verdict of guilty against the defendant Joseph P. Andrade (Andrade) on indict *654 ments charging him with unarmed robbery, assault and battery, and unauthorized use of a motor vehicle. Andrade attacks his conviction of unarmed robbery (the other convictions were placed on file) on the grounds that: (1) a pretrial confession should have been suppressed; (2) evidence of an impermissibly suggestive photographic identification procedure was received in evidence; and (3) mug shots of Andrade and his brother should not have gone to the jury, and, in all events, were inadequately sanitized. We conclude that there was no error.
1. Validity of the pretrial confession. The crimes occurred in Wareham on the evening of April 8, 1973; the victim was a cab driver, one Demers. His assailant was a passenger who demanded Demers’ money, received it, and thereupon knocked Demers senseless and dragged him from his cab.
Three days later, on April 11, 1973, a detective of the Wareham police department, Jack B. Russell, was engaged in an investigation involving a break into a school. The trail of that inquiry led to the defendant and his brother, both of whom were arrested that day and detained at the Wareham police station. While thus at the police station, Detective Russell told Andrade he wished to question him about the taxicab matter and gave him all the elements of a Miranda warning. The motion judge at the suppression hearing found that Andrade understood the warning. Detective Russell told Andrade that the taxicab had been found 100 yards to the rear of his home; that a black youth with a “short afro” had been seen driving the cab after the robbery of Demers; that the car had been dusted for fingerprints; and that his picture would be put in a mug book to be taken to Demers and viewed by him. Asked by Detective Russell if he had anything to say, Andrade said, “I done it.”
At that point Detective Russell called in Sergeant Barrett of the Wareham police, to whom he said that *655 Andrade wanted to make a statement. Sergeant Barrett read the Miranda warning to Andrade from a card. The latter said he understood his rights and gave a statement admitting the crimes, which Detective Russell wrote down in longhand and to which Andrade subscribed by his signature.
The contentions which Andrade raised at the suppression hearing, and which he presses on appeal, are that the coercive environment which surrounded the interrogation and his limited education (not beyond the fifth grade) precluded an intelligent and voluntary waiver of his Miranda rights. See
Miranda
v.
Arizona,
Our examination of the record persuades us that the trial judge carefully considered the applicable principles. He chose to disbelieve, as he was entitled to, Andrade’s claim, denied by Detective Russell, that Russell had offered Andrade help on the breaking and entering charge in exchange for a confession on the assault and battery case. Although Andrade had only a fifth-grade educa
*656
tion, the judge had observed him and had concluded that Andrade “understood his rights and everything that was said to him or that he said in the Wareham police station on April 11, 1973.” Age alone is not a controlling factor. Cf.
Commonwealth
v.
Cain,
Contrary to the defendant’s assertion, there is no requirement that a waiver be written.
1
North Carolina
v.
Butler,
We are of the opinion that the judge’s finding on the voluntariness of the waiver of the right to remain silent ought not to be disturbed. In coming to this determination we have applied the standards set out in
Commonwealth
v.
Meehan,
2. Suggestiveness of the pretrial court identification. Two days after the attack on Demers, Detective Russell visited him in the hospital and showed him a mug book containing pictures of approximately seventy persons who had been arrested in Wareham. Demers selected, as resembling his assailant, a photograph of the defendant’s brother. On the next day Detective Russell returned to the hospital with the same mug book into which he had, in the meantime, inserted Andrade’s pic *657 ture next to that of his brother. Otherwise, the book was unaltered. Demers identified Andrade as the assailant.
At trial, the Commonwealth contented itself with an in-court identification by Demers of the defendant as the man who had robbed and beaten him. ‘Even if the pretrial identification were unnecessarily suggestive, the subsequent identification at trial would be excluded ‘only if the photographic identification [were] so impermissibly suggestive as to give rise to a very substantial likelihood of irreparable misidentification.’ ”
Commonwealth
v.
Venios,
Nor was the photographic array impermissibly suggestive on the basis of the criteria and procedures described in
Commonwealth
v.
Murphy,
3.
Whether the mug shots should have gone to the jury and whether they were adequately sanitized.
The photographs of Andrade and his brother which Demers had picked out of the mug book were offered during the prosecution’s rebuttal of the defense’s attack on Demers’ capacity to make an identification of Andrade. In those circumstances, the admission in evidence of the mug shots themselves was justified.
Commonwealth
v.
Washburn,
Judgment affirmed.
Notes
Both parties concede that the presence of a written confession does not preclude inquiry into whether the waiver was voluntary.
