On June 26, 2006, a Berkshire County grand jury indicted the defendant as a youthful offender pursuant to G. L. c. 119, § 54, alleging that the juvenile was an accessory after the fact, G. L. c. 274, § 4. This indictment was dismissed by a judge of the Juvenile Court, and the Commonwealth appeals.2

General Laws c. 119, § 54, as amended by St. 1996, c. 200, *19§ 2, grants the government the authority to obtain an indictment in juvenile proceedings provided an alleged offender has, inter alia, “committed an offense against a law of the Commonwealth . . . [that] involves the infliction or threat of serious bodily harm.” In determining whether any particular offense “involves the infliction or threat of serious bodily harm,” it is necessary to determine whether the “conduct constituting the offense itself” involves the form of harm described in the statute. Commonwealth v. Clint C., 430 Mass. 219, 225 (1999). That is to say, it is necessary to determine actual conduct undertaken by the defendant, rather than merely the elements of the underlying crime, in determining whether an indictment is authorized under § 54.3

Here, the Commonwealth sought to bring the offense underlying the allegation of delinquency within G. L. c. 274, § 4, as amended by St. 1943, c. 488, § 1, which provides that “[whoever, after the commission of a felony, harbors, conceals, maintains or assists the principal ... or gives such offender any other aid . . . with the intent that he shall avoid or escape . . . arrest . . . shall be an accessory after the fact, and ... be punished.” Based on the evidence presented in the Juvenile Court proceedings, the judge below could have found as follows: the juvenile was present in a house where her boyfriend, Luis Torres, shot another man during a fight, wounding him. The juvenile then fled with Torres and another man, Michael Pinel. The trio went to a nearby convenience store, where the juvenile arranged for a taxicab to transport the group to an apartment in a neighboring town. When police tracked Torres to that apartment, the juvenile initially denied that Torres was present.

The Commonwealth contends — as it must in order to provide a basis for the indictment obtained under § 54 — that by abetting Torres’s escape and subsequently helping to conceal him from police, the juvenile’s conduct “involve[d] the infliction or threat of serious bodily harm.”4 In so characterizing the juve*20nile’s actions, the Commonwealth essentially ascribes to the juvenile vicarious liability for the violent act committed by Torres. We disagree with this approach.

In its argument, and by means of the cases on which it relies,5 the Commonwealth seeks to conflate the form of accessorial liability with which the defendant is charged here with general joint venture liability or liability as an accessory before the fact and, thereby, place her on the same footing as Torres. Such comparisons, however, are inapposite.6 There is no question that the law in the Commonwealth, as in most jurisdictions, equates the culpability of a joint venturer or accessory before the fact with the culpability of the principal. As set out in G. L. c. 274, § 2, as amended through St. 1973, c. 529, § 1, “[wjhoever aids in the commission of a felony, or is an accessory thereto before the fact . . . shall be punished in the manner provided for the punishment of the principal felon.” See G. L. c. 274, § 3. Likewise, a joint venturer is subject to the same penalties as the principal whom he or she assists (or stands ready to assist). See, e.g., Commonwealth v. Williams, 450 Mass. 894, 898 (2008). By contrast, under G. L. c. 274, § 4, an accessory after the fact (i.e., the charge underlying the youthful offender indictment here), is subject to a maximum sentence of seven years regardless of the maximum punishment associated with the offense committed by the principal.

This distinction derives, inter alia, from the fact that an ac*21cessory before the fact or a joint venturer ordinarily must share the same mental state required for conviction of the principal, and also be involved (or be ready, willing, and able to become involved) in the planning or execution of the crime. See G. L. c. 274, §§ 2 & 3; Commonwealth v. Chhim, 447 Mass. 370, 378 (2006). However, an accessory after the fact need not, and generally does not, have any advance knowledge of the principal’s intent to commit an offense and is, by definition, not involved in its planning or execution; rather, an accessory after the fact need merely “know the identity of the principal perpetrator and have knowledge of the ‘substantial facts of the felonious crime’ that the principal committed” and, possessed of such knowledge, aid the principal in avoiding punishment. Commonwealth v. Perez, 437 Mass. 186, 190 (2002), quoting from Commonwealth v. Devlin, 366 Mass. 132, 134 (1974).

On the basis of this crucial distinction, we reject the Commonwealth’s argument that Torres’s violent acts must be imputed to the juvenile in assessing her vulnerability to indictment under G. L. c. 119, § 54. Accordingly, and consistent with the decision in Clint C., supra, we look only to the juvenile’s own conduct in assessing the applicability of that provision. Her actions in facilitating Torres’s escape and avoiding arrest did not involve the requisite “infliction or threat of serious bodily harm” described in the statute. See Commonwealth v. Quincy Q., 434 Mass. 859, 863 (2001) (youthful offender indictment dismissed where based on charges of indecent assault and battery upon a child where the assault consisted of touching only and so did not involve the infliction or threat of infliction of bodily harm). Needless to say, the outcome may well have been different had the juvenile been charged as an accessory before the fact or joint venturer. However, that is not the situation here. The Juvenile Court’s order dismissing the youthful offender indictment is affirmed.

So ordered.