(dissenting, with whom Spina, J., joins). The court’s decision will seriously impede the prosecution of dangerous and violent juvenile offenders. To give just one example — as a result of the decision, a prosecutor, in a case involving violent crimes committed by juvenile gang members (a common occurrence in today’s society) will not be able to offer immunity to one gang member in exchange for his testimony against the others, a situation which may stymie or prevent the prosecution.1 I conclude that the Legislature could not have intended to withhold the power to grant immunity from Juvenile Court judges, and thus undermine the goals of the Youthful Offender Act. I, therefore, dissent.
The court’s interpretation fails to give full effect to the *525language of § 56 (d), contrary to the accepted principle of interpretation that all the words in a statute are to be given meaning. See Hallett v. Contributory Retirement Appeal Bd., 431 Mass. 66, 69 (2000). By so doing, the court carves out an unwarranted exception to the provision in § 56 (d) that Juvenile Court judges in jury sessions shall have all the powers and duties of Superior Court judges sitting in criminal cases. Under the court’s construction, § 56 (d) now reads as providing Juvenile Court judges in jury sessions with the powers of Superior Court judges in the trial and disposition of criminal cases except for the power to enter an order granting a witness immunity. Thus, the court “make[s] [part of the] statutory language meaningless,” an undesirable result. See Commonwealth v. Maher, 408 Mass. 34, 37 (1990).
In my view, § 20E of the immunity statute, and § 56 (d) of G. L. c. 119, can be read together.2 It should be assumed that the Legislature was aware of existing statutes when it enacted § 20E, Mathewson v. Contributory Retirement Appeal Bd., 335 Mass. 610, 614 (1957), and every effort should be made to interpret § 20E in harmony with § 56 (d), in order to create a consistent body of law. See Charland v. Muzi Motors, Inc., 417 Mass. 580, 582-583 (1994), and cases cited. “The Legislature is ‘presumed to understand and intend all consequences’ of its acts.” Id. at 583, quoting Boston Water & Sewer Comm’n v. Metropolitan Dist. Comm’n, 408 Mass. 572, 578 (1990). In 1998, when the Legislature amended the immunity statute to authorize Superior Court judges to immunize witnesses in criminal proceedings, it must have been cognizant that § 56 (d), enacted not two years earlier, continued in effect the provision that Juvenile Court judges possessed all the authority of Superior Court judges in the trial and disposition of criminal cases. It follows logically that the Legislature intended Juvenile Court judges to exercise immunity powers, because the Legislature presumably understood that, by providing Superior Court judges with the authority to immunize witnesses, it was *526providing Juvenile Court judges with this power as well.
This conclusion is consistent with, and supported by, the climate that existed at the time the Legislature amended the immunity statute. The Youthful Offender Act, passed shortly before § 20E, was an emphatic and strong legislative response to “the prevalent societal issue of juvenile violence.” R.L. Ireland, Juvenile Law § 2, at 8 (Supp. 1999). That Act’s new provisions reflected the more conservative view that the Legislature had adopted toward juveniles who commit violent crimes (e.g., confinement in a State prison or house of correction, G. L. c. 119, § 58; mandatory penalties for certain weapons violations, id.\ court proceedings open to the public, G. L. c. 119, § 65; court records open to public inspection, G. L. c. 119, § 60A). See R.L. Ireland, supra at 8-9. The Legislature obviously concluded that violent juvenile offenders should be prosecuted in the Juvenile Court, essentially in the same manner as adults in the Superior Court.3 Because the Legislature has broadened the jurisdiction, and concomitant authority, of Juvenile Court judges to confront escalating violent juvenile crime, it would be inconsistent for the Legislature, only two years later, to confine the power to immunize witnesses to Superior Court judges and thereby deprive prosecutors of a vital crime fighting tool.4 The order below should be vacated and the case remanded with directions that the Commonwealth’s application for immunity for the witness should be heard, and, if appropriate, granted.
With the exception of prosecutions for murder, the impediment to prosecution described above could affect violent crimes such as arson, armed burglary, armed robbery, assaults, extortion, a variety of firearm violations, witness and juror intimidation, kidnapping, violations of the narcotic or harmful drug laws, receiving stolen property, rape and other sexual assaults, subornation of perjury, and conspiracy or attempt or solicitation to commit these offenses. This list is not exhaustive of the offenses set forth in G. L. c. 233, § 20D, but it provides an enumeration of many crimes often committed by gangs of juveniles which could result in prosecution under the Youthful Offender Act, and in connection with which a prosecutor could desire or need the assistance of a grant of immunity in order to try the dangerous juvenile or juveniles who committed the crime or crimes.
It is not necessary to construe § 20E strictly against the Commonwealth. See Commonwealth v. Carrion, 431 Mass. 44, 45-46 (2000) (rule of lenity requires that ambiguous language in penal statute be construed in favor of defendant). Section 20E does not define criminal conduct or prescribe punishment, and, therefore, is not a penal statute. See id. at 46.
For example, many of the discovery provisions applicable to Superior Court proceedings were also made applicable to Juvenile Court proceedings. G. L. c. 119, § 55A.
The witness for whom immunity is sought argues that an interpretation of § 20E, in light of § 56 (¿Q, would create an “anomaly,” by which District Court judges would have the authority to issue an order granting immunity in juvenile sessions, but those same District Court judges could not do so in any other proceedings. There is no anomaly. District Court judges have the authority to grant immunity in other proceedings pursuant to G. L. c. 218, §§ 26A and 27A (providing District Court judges presiding over jury and jury-waived criminal trials with “all the powers and duties which a justice sitting in the superior court department has and may exercise in the trial and disposition of criminal cases”). The powers, including the power to grant immunity, would apply to the relatively small category of cases, identified in § 20D, that fall within District Court criminal jurisdiction.