"Legislatures may not retroactively alter the definition of crimes or increase the punishment for criminal acts." (Collins v. Youngblood (1990) 497 U.S. 37.) Both the federal and state Constitutions prohibit ex post facto laws. (U.S. Const., art. I, 10, cl. 1; Cal. Const., art. I, 9; Youngblood, at pp. 41-42 111 L.Ed.2d at pp. 38-39; Tapia v. Superior Court (1991) 53 Cal.3d 282, 288.) "The standard for determining whether a law violates the ex post facto clause has two components, 'a law must be retroactive--that is, "it must apply to events occurring before its enactment" -- and it "must disadvantage the offender affected by it" . . . by altering the definition of criminal conduct or increasing the punishment for the crime. . . .'" (People v. Delgado(2006) 140 Cal.App.4th 1157, 1164.) To determine whether a law is punitive for ex post facto purposes, "we first examine whether the statute's effect is to punish defendant for past offenses" and "next we examine the purpose of the statute." (People v. McVickers (1992) 4 Cal.4th 81, 87, 88.) The ex post facto clause of the California Constitution is to be analyzed identically to that of the United States Constitution. ( People v. McVickers (1992) 4 Cal.4th 81, 84, overruled on another issue in Collins v. Youngblood (1990) 497 U.S. 37, 42-52.) There are four categories of ex post facto laws (Calder v. Bull (1798) 3 U.S. 386, 390 (Calder)): 1st. Every law that makes an action done before the passing of the law, and which was innocent when done, criminal; and punishes such action. 2d. Every law that aggravates a crime, or makes it greater than it was, when committed. 3d. Every law that changes the punishment, and inflicts a greater punishment, than the law annexed to the crime, when committed. 4th. Every law that alters the legal rules of evidence, and receives less, or different testimony, than the law required at the time of the commission of the offense, in order to convict the offender." (Ibid.)