The merger doctrine was articulated in People v. Ireland (1969) 70 Cal.2d 522. In that case, the California Supreme Court adopted the merger doctrine, holding that the trial court erred by instructing a jury on second degree felony murder based on the felony of assault with a deadly weapon (Penal Code 245), because the felony merged with the resulting homicide. Prior to Ireland, the "merger" doctrine developed in other jurisdictions as a shorthand explanation for the conclusion that the felony-murder rule should not be applied in circumstances where the only predicate felony committed by the defendant was assault. (People v. Hansen (1994) 9 Cal.4th 300.) "The name of the doctrine derived from the characterization of the assault as an offense that 'merged' with the resulting homicide." (Ibid.) In Ireland, the California Supreme Court discussed the merger rule. In that case, a husband shot his wife, and the court instructed on second degree felony murder based on the predicate felony of section 245, assault with a deadly weapon. The court refused to extend the second degree felony-murder rule to that case because it would extend the rule beyond any rational purpose it was intended to serve. The court stated: "To allow such use of the felony-murder rule would effectively preclude the jury from considering the issue of malice aforethought in all cases wherein homicide has been committed as a result of a felonious assault--a category which includes the great majority of all homicides." (Ireland, supra, 70 Cal.2d at p. 539.) The court concluded that a trial court may not instruct the jury with second degree felony murder when the instruction is "based upon a felony which is an integral part of the homicide and which the evidence produced by the prosecution shows to be an offense included in fact within the offense charged." (Ibid.) People v. Smith (1984) 35 Cal.3d 798, extended the People v. Ireland (1969) 70 Cal.2d 522 merger rule to a case in which the predicate felony was felony child abuse in violation of section 273a. The California Supreme Court noted that a defendant may be convicted of section 273a due to active conduct, i.e., child abuse by direct assault, and passive conduct, i.e., child endangering by extreme neglect. In Smith, the child died because of direct assault. The court stated: "In the present case the homicide was the result of child abuse of the assaultive variety. Thus, the underlying felony was unquestionably an 'integral part of' and 'included in fact' in the homicide within the meaning of Ireland." (Smith, at p. 806.) The court noted there was no independent purpose for the conduct and, like Ireland, "the purpose here was the very assault that resulted in death." Smith noted, "The elements of section 245 and the offense here are strikingly similar; the principal difference is that the assault prohibited by section 273a is committed on a child." (Smith, supra, 35 Cal.3d at p. 807.) The court earlier noted that the felony-murder rule is a disfavored doctrine and should be interpreted narrowly " 'consistent with its ostensible purpose--which is to deter those engaged in felonies from killing negligently or accidentally.' " (Id. at p. 803.) Importantly, Smith also stated, "by its very definition felony child abuse occurs only 'under circumstances or conditions likely to produce great bodily harm or death.' It is untenable to assert that there is an independent design when the crime of felony child abuse of the assaultive variety is willfully committed under such circumstances." (Id. at p. 808.) Smith thus applied the merger rule to a situation in which the predicate felony was not expressly referred to as a violation of section 245, but the predicate felony was of the "assaultive variety" (Smith, at p. 808).