OPINION BY LALLY-GREEN, J.

¶ 1 Appellant, William Irving Davis, appeals from the order entered April 20, 1999, denying his first petition for relief under the Post Conviction Relief Act (PCRA), 42 Pa.C.S.A. §§ 9541-9546. We reverse and remand for resentencing.

¶ 2 The facts underlying Appellant's conviction were summarized by this Court on direct appeal as follows:

On October 16, 1984, Jobe Wright, Terrance George and Appellant drove through the Monroeville Mall parking lot in a red Chevrolet Camaro. George reached out of the car and snatched the purse of Marjorie Wilson. Appellant and his companions then exited the parking lot and proceeded along Route 22 west-bound towards Pittsburgh. After traveling approximately one-half mile, Appellant, who was driving, lost control of the vehicle and crossed over into the lanes of oncoming traffic. In the tragic collision which ensued, an elderly couple [(Elmer and Sarah Burger)] died. Terrance George also lost his life. Appellant fled the scene of the accident on foot. He turned himself in to police several days later.

Docket Entry 46 at 1-2; Commonwealth v. Davis, 565 A.2d 458, 459 (Pa.Super. 1989), appeal denied, 525 Pa. 595, 575 A.2d 561 (1990).

¶ 3 On the date of the offense, October 16, 1984, a single auto accident caused by criminal behavior was considered one offense against the Commonwealth, exposing the defendant to only one penalty, regardless of the number of victims involved (the "one sentence rule"). See, e.g., Commonwealth v. Frisbie, 464 A.2d 1283, 1288-1289 (Pa.Super. 1983) ("Frisbie I").

¶ 4 On December 13, 1984, Appellant was charged by information as follows:

CC #8411736 — Robbery Criminal Conspiracy Theft by Unlawful Taking

CC #8411789 — Homicide (Elmer Burger) Homicide (Sarah Burger) Homicide by Vehicle (Terrance George) Homicide by Vehicle (Elmer Burger) Homicide by Vehicle (Sarah Burger)

CC #8412440 — Recklessly Endangering Another Person ("REAP") Receiving Stolen Property Careless Driving Driving at an Unsafe Speed

¶ 5 On December 18, 1984, approximately two months after the incident in question, our Supreme Court reversed this Court's decision in Frisbie I. Specifically, the Court held that one criminal incident involving multiple victims could be considered more than one crime, carrying more than one penalty, depending on the language of the criminal statute at issue (the "multiple sentence rule"). Commonwealth v. Frisbie, 485 A.2d 1098, 1099-1100 (Pa. 1984) ("Frisbie II").

¶ 6 Appellant's case proceeded to trial on October 22-29, 1985. On October 31, 1985, Appellant was convicted of all charges. Docket Entries 26-28. The homicide charges were graded as third degree murder. Docket Entry 27. On October 7, 1986, Appellant was sentenced to an aggregate prison term of 18 1/4 years to 36 1/2 years. Docket Entries 1-3.

¶ 7 At this point, we will briefly identify two aspects of the sentence that Appellant challenges herein. First, the sentence included a term of 7 1/2 to 15 years for the murder of Elmer Burger, and a second consecutive term of 7 1/2 to 15 years for the murder of Sarah Burger. Docket Entry 1. Second, the sentence included two consecutive prison terms related to the death of victim Sarah Burger (the aforementioned 7 1/2 to 15 years for third degree murder, and a consecutive term of 2 1/2 to 5 years for homicide by vehicle).

Id.

¶ 8 On October 23, 1986, the sentencing court denied Appellant's Motion to Modify Sentence. Docket Entry 76; N.T., 10/23/86, at 35. This Court affirmed the judgment of sentence on October 16, 1989. Docket Entry 46; Davis, 565 A.2d 458. The Pennsylvania Supreme Court denied allowance of appeal on May 2, 1990. Docket Entry 46; Davis, 575 A.2d 561.

¶ 9 On February 12, 1996, Appellant filed a pro se PCRA petition. Docket Entry 52. A counseled, amended PCRA petition was filed on June 26, 1998. Docket Entries 58-60. The PCRA court dismissed Appellant's petition on April 20, 1999. Docket Entry 66. This appeal followed.

¶ 10 Appellant raises the following issues:

A. Are Appellant's sentences illegal because, under the sentencing law which prevailed at the time of the offenses, it was unlawful to impose multiple punishments for one vehicular act?

B. Are Appellant's sentences illegal because, under the sentencing law which prevailed at the time of the offenses, the Supreme Court regarded homicide by vehicle as a lesser included offense of third degree murder and, therefore, those offenses should have merged?

Appellant's Brief at 9.

¶ 11 Our review of a PCRA court's grant or denial of relief is limited to examining whether the court's determination is supported by the evidence and whether it is free of legal error. Commonwealth v. Walker, 721 A.2d 380, 381 (Pa.Super. 1998). Under the PCRA, a petitioner must plead and prove by a preponderance of the evidence that his claim falls within one of seven specific categories of error, including "[t]he imposition of a sentence greater than the lawful maximum." 42 Pa.C.S.A. § 9543(a)(2) (vii).

¶ 12 Both of Appellant's claims are cognizable under the PCRA because they involve allegations that the court imposed separate sentences on charges that should have merged. Commonwealth v. Lehr, 583 A.2d 1234, 1236 (Pa.Super. 1990); see also, Commonwealth v. Neupert, 684 A.2d 627, 628-629 (Pa.Super. 1996). Moreover, challenges to the legality of a sentence cannot be waived. Commonwealth v. Hockenberry, 689 A.2d 283, 288 (Pa.Super. 1997), appeal denied, 695 A.2d 784 (Pa. 1997). Accordingly, these issues are preserved even though Appellant did not raise them on direct appeal.

¶ 13 First, Appellant argues that the trial court violated his due process rights by sentencing him in accordance with the multiple sentence rule announced in Frisbie II. Specifically, he asserts that: (1) Frisbie II represented a new and unexpected change in the law; and (2) that retroactive application of Frisbie II exposed him to a greater prison term than he could have expected at the time of the offense. Appellant concludes that he should be resentenced under the one sentence rule which was in effect at the time of the offense.

¶ 14 Appellant's due process claim has its origins in the ex post facto clauses of the United States Constitution and the Pennsylvania Constitution. U.S. Const. Art. 1, § 10; Pa. Const. Art. 1, § 17.

¶ 15 The United States Constitution provides that "no State shall . . . pass any . . . ex post facto Law. . . ." U.S. Const. Art. 1, § 10. The Pennsylvania Constitution provides that "no ex post facto law . . . shall be passed." Pa. Const. Art. 1, § 17. The Pennsylvania Constitution provides the same ex post facto protections as the United States Constitution. Commonwealth v. Fisher, 741 A.2d 1234, 1238 (Pa. 1999). Because there is no appreciable difference between the two constitutional provisions or our Courts' analysis thereof, we will refer to them collectively as "the ex post facto clause".

¶ 16 Before we turn directly to the due process claim, we will briefly review relevant ex post facto principles. In 1798, the United States Supreme Court identified four types of prohibited ex post facto laws:

1st. Every law that makes an action done before passing of the law, and which was innocent when done, criminal; and punishes such action. 2nd. Every law that aggravates a crime, or makes it greater than it was, when committed. 3rd. 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 offence, in order to convict the offender.

Calder v. Bull, 3 U.S. 386, 390 (1798) (emphasis added). These four categories are still recognized today. Collins v. Youngblood, 497 U.S. 37, 42 (1990); Fisher, 741 A.2d at 1238.

¶ 17 We recently set forth other relevant ex post facto principles as follows:

The bulk of our ex post facto jurisprudence has involved claims that a law has inflicted a "a greater punishment, than the law annexed to the crime, when committed." Calder[.] We have explained that such laws implicate the central concerns of the Ex Post Facto Clause: "the lack of fair notice and governmental restraint when the legislature increases punishment beyond what was prescribed when the crime was consummated." Weaver v. Graham, 450 U.S. 24, 30 (1981).

To fall within the ex post facto prohibition, a law must be retrospective — that is "it must apply to events occurring before its enactment" — and it "must disadvantage the offender affected by it" id., at 29[,] by altering the definition of criminal conduct or increasing the punishment for the crime, see Collins[,] 497 U.S. [at 50].

Commonwealth v. Kline, 695 A.2d 872, 874 (Pa.Super. 1997), appeal denied, 552 Pa. 694, 716 A.2d 1248 (1998).

¶ 18 Appellant's due process claim is not, strictly speaking, an ex post facto claim. That phrase is a term of art applying to statutes passed by legislatures. Marks v. United States, 430 U.S. 188, 191 (1977).

¶ 19 Some judicial enlargements of a criminal statute do, however, operate, like ex post facto laws. The United States Supreme Court has held that:

[A]n unforeseeable judicial enlargement of a criminal statute, applied retroactively, operates precisely like an ex post facto law, such as Art. I, § 10, of the Constitution forbids. . . . [Thus], if a state legislature is barred by the Ex Post Facto Clause from passing such a law, it must follow that a State Supreme Court is barred by the Due Process Clause from achieving precisely the same result by judicial construction.

Bouie v. City of Columbia, 378 U.S. 347, 353 (1964); see also, Marks, 430 U.S. at 192. Summarizing, state courts may not unforeseeably and retroactively apply case law that increases the penalty for criminal conduct.

¶ 20 We now turn to the question of whether Frisbie II was an unforeseeable change in the law. This issue raises two somewhat interrelated sub-issues: (1) change, and (2) foreseeability. Our standard of review is plenary. Helton, 930 F.2d at 1044.

¶ 21 The first issue is whether Frisbie II "changed" the law of Frisbie I. We begin with this Court's decision in Frisbie I, decided on August 12, 1983, slightly more than one year before the offense at issue. In Frisbie I, the defendant was convicted and sentenced on nine separate counts of REAP after he drove his vehicle through a crowd of people. Frisbie I, 464 A.2d at 1285. In deciding that the defendant should have been sentenced on only one count of REAP, this Court reasoned as follows:

¶ 22 In Commonwealth v. Walker, 468 Pa. 323, 362 A.2d 227 (1976), our Supreme Court stated that the:

[A]nalysis of duplicitous sentence questions has traditionally revolved around the concept of injury to the sovereign, in this case the Commonwealth. One of the purposes of the criminal law is to punish offenses against the Commonwealth, as defined by the Legislature, and it follows that, `[t]he criminal prosecution is for the injury done to the Commonwealth, and not for the injury done to the individual who may, if entitled, obtain redress through a civil action. Where there is but one act of cause of injury, or death of a number of persons, there is but one injury to the Commonwealth, but where the acts or causes are separate, they are separate injuries to the peace and dignity of the Commonwealth . . .'

Id. 468 Pa. at 331, 362 A.2d at 231 (citations omitted). When there has been a single injury to the "peace and dignity of the Commonwealth," it is beyond the power of a sentencing court to impose multiple sentences upon a defendant. Commonwealth v. Walker, supra; Commonwealth v. Reynolds, 256 Pa. Super. 259, 389 A.2d 1113 (1978); Commonwealth v. Speelman, 235 Pa. Super. 109, 341 A.2d 138 (1975); Commonwealth ex rel. Brockway v. Keenan, 180 Pa. Super. 78, 118 A.2d 255 (1955). See also Commonwealth v. Crocker, 280 Pa. Super. 470, 421 A.2d 818 (1980); Commonwealth v. Lezinsky, 264 Pa. Super. 476, 400 A.2d 184 (1979).

We have determined from the record that the nine counts of recklessly endangering another person lodged against appellant were founded on a single unlawful act committed by appellant. The record reveals that Appellant propelled his vehicle forward through a crowd of persons causing injury to numerous persons simultaneously. While this single action of appellant may constitute more than one criminal cause of action for recklessly endangering another person, it may still support but one sentence. See Commonwealth v. Cox, 209 Pa. Super. 457, 228 A.2d 30 (1967). See also Commonwealth v. Speelman, supra. Accordingly, we will vacate the sentences imposed upon appellant for all counts of recklessly endangering another person.

Id. at 1288-1289.

¶ 23 In Speelman, we noted that the one sentence rule had "long been the law". Speelman, 341 A.2d at 141, citing, inter alia, Commonwealth v. Ernesto, 93 Pa. Super. 339 (1928). Moreover, in Reynolds, we specifically rejected the proposition that the Crimes Code required courts to adopt the multiple sentence rule:

The courts have reasoned that if there is a single criminal act there is a single injury to the Commonwealth. Consequently, the courts of Pennsylvania have no power to impose more than one sentence on a single unlawful act. [Speelman, supra; Cox, supra; Keenan, supra; McCord, supra; Ernesto, supra.] The Commonwealth argues that the enactment of the Crimes Code dictates a different result. However, Pennsylvania law has been quite clear on this issue since 1928. If the legislature desired to change the law, it should have specifically done so. Commonwealth v. Miller, 469 Pa. 24, 364 A.2d 886 (1976). Because there has been no explicit change in this well-settled doctrine, we will continue to apply it.

Reynolds, 389 A.2d at 1123.

¶ 24 In Frisbie II, our Supreme Court reversed Frisbie I and announced the "multiple sentence" rule. In doing so, the Court adopted the argument which this Court expressly rejected in Reynolds: namely, that the issue of multiple punishments should be resolved by reference to the language of the specific statute at issue. Frisbie II, 485 A.2d at 1100. In other words, if statute prohibits injury to "a person", then the defendant may be punished separately for each victim. Id. at 1100. On the other hand, if the statute prohibits injury to "one or more persons", then the defendant may be punished only once, regardless of the number of victims. Id.

¶ 25 In announcing this rule, the Court expressly overruled its own precedent in Walker, which described a criminal act as one offense against the Commonwealth. Id. at 1099. By implication, the Court also abrogated the long line of cases discussed in Frisbie I, et al., which set forth the "one sentence" rule. Because Frisbie II overruled Supreme Court precedent and overturned a longstanding principle of law in favor of a new rationale, we conclude that Frisbie II represented a change in the law.

¶ 26 We must now decide whether the new rule was foreseeable. "The test for determining whether the retroactive application of a judicial decision violates due process is essentially one of foreseeability." Johnson v. Kindt, 158 F.3d 1060, 1063 (10th Cir. 1998), cert. denied, 525 U.S. 1075 (1999). The critical issue is what the defendant could have anticipated on the date of the offense. Weaver, 450 U.S. at 30-31. The Tenth Circuit Court of Appeals recently suggested the following guidelines for determining whether a new decision is unforeseeable:

A judicial construction of a statute is unforeseeable if it is "unexpected and indefensible by reference to the law which had been expressed prior to the conduct at issue." Bouie, 378 U.S. at 354. Unforeseeable judicial decisions include expansion of a statute narrow and precise on its face beyond those terms, the overruling of precedent, Devine, 866 F.2d at 345; or when "an in-depth inquiry by a dedicated and educated student of the relevant law would have revealed nothing to foreshadow the controlling court opinion." Id.

Johnson, 158 F.3d at 1063 (citation omitted).

¶ 27 As noted above, in announcing Frisbie II, the Court overruled its own precedent and abrogated a line of cases extending back as far as 1928. Moreover, we have discovered no Supreme Court case which predicted, anticipated, or foreshadowed such action. In short, at the time of the offense, Appellant could have reasonably expected to be sentenced under the longstanding rule announced in Frisbie I. For these reasons, we conclude that Frisbie II was unforeseeable.

¶ 28 Finally, the record reveals that by applying the "multiple sentence" rule, the trial court prejudiced Appellant by imposing a greater sentence than could have imposed under the prior law. For all of these reasons, we conclude that the Appellant's sentence violated due process. We are constrained to remand for resentencing.

¶ 29 The Commonwealth raises three counterarguments to Appellant's due process claim. First, the Commonwealth argues that Frisbie II did not announce new law because, at the time of the offense, the Crimes Code allowed for application of the "multiple sentence" rule. Commonwealth's Brief at 15. In other words, Frisbie II simply clarified that courts should look to the language of the existing Crimes Code when determining whether multiple injuries warrant multiple punishments. Id. at 16. We are not persuaded by this argument. For the reasons set forth above, we conclude that Frisbie II represented a clear break from past precedent and not a clarification of existing law.

¶ 30 Second, the Commonwealth suggests that Frisbie II should be applied retroactively to Appellant because Frisbie II did not specifically declare that the new rule should be applied prospectively. Commonwealth's Brief at 16, citing Commonwealth v. Tizer, 684 A.2d 597, 601 (Pa.Super. 1996) ("unless [a new court decision] specifically declares the ruling to be prospective only, the new rule is to applied retroactively to cases where the issue in question is properly preserved at all stages of adjudication up to and including any direct appeal."). While we recognize this general rule, we cannot apply Frisbie II retroactively because doing so would result in a due process violation.

¶ 31 Third, the Commonwealth argues that it is untenable to find a due process violation in this case because doing so would call into question the cases of Commonwealth v. Zaengle, 480 A.2d 1224 (Pa.Super. 1984); Commonwealth v. Sheffy, 505 A.2d 604 (Pa.Super. 1986), cert. denied, 479 U.S. 1097 (1987); and Commonwealth v. Yates, 562 A.2d 908 (Pa.Super. 1989). We will briefly outline the procedural history of each case.

¶ 32 In Zaengle, the trial court imposed multiple sentences arising out of an auto accident which resulted in the death of three people. Zaengle, 480 A.2d at 1225-1226. As in the instant case, the crime took place when the "one sentence" rule was still in effect. Id. at 1225. On August 10, 1984, this Court vacated the sentences and remanded for resentencing pursuant to the "one sentence" rule. Id. at 1227-1228. Two months later, our Supreme Court issued Frisbie II. Our Supreme Court then remanded the Zaengle case for proceedings consistent with Frisbie II. Zaengle, 497 A.2d 1335, 1336 (Pa.Super. 1985). On remand, this Court reinstated the multiple sentences originally imposed by the trial court. Id. No due process concerns were identified with this action.

¶ 33 In Sheffy, the trial court applied the "one sentence" rule to a defendant who had killed four victims in an arson. Sheffy, 505 A.2d at 609. The "one sentence" rule was in effect at the time of the crime. Id. Five months after sentencing, our Supreme Court issued Frisbie II. After noting that our Supreme Court had changed the law in this area, we invited the trial court to consider resentencing Sheffy in accordance with Frisbie II. Id. at 609-610. Again, no due process concerns were identified.

¶ 34 In Yates, the trial court imposed multiple sentences to a defendant who had injured two victims with a single shotgun blast. Yates, 562 A.2d at 909. The "one sentence" rule was in effect at the time of the crime. Id. On appeal, this Court rejected the defendant's argument that the "one sentence" rule should apply. Id. at 909-910, citing Frisbie II, 485 A.2d at 1100.

¶ 35 The Commonwealth suggests that finding a due process violation in the instant case would be inconsistent with the outcomes of Zaengle, Sheffy, and Yates. We disagree. So far as can be discerned from those opinions, the defendants failed to identify and raise any due process concerns arising out of the retroactive application of Frisbie II. Because the due process issue raised here was not raised in Zaengle, Sheffy, or Yates, those cases do not control the instant case or compel a different result.

¶ 36 We now briefly turn to Appellant's second issue on appeal: that Appellant's sentence for homicide by vehicle with respect to victim Sarah Burger should have merged with his sentence for third degree murder with respect to the same victim.

¶ 37 At the time of Appellant's offense, homicide by vehicle merged with involuntary manslaughter for sentencing purposes. Commonwealth v. Houtz, 437 A.2d 385, 386-387 (Pa. 1981); see also, Commonwealth v. Comer, 716 A.2d 593, 599 (Pa. 1998). Moreover, our Courts have held that involuntary manslaughter is a lesser included offense of third degree murder. Commonwealth v. Polimeni, 378 A.2d 1189, 1193 (Pa. 1977); In Interest of Smith, 579 A.2d 889, 896 (Pa.Super. 1990); appeal denied, 527 Pa. 610, 590 A.2d 296 (1991). Appellant argues that homicide by vehicle must, therefore, necessarily merge with third degree murder under the facts of this case. The Commonwealth does not seriously contest this position, and we agree with Appellant's argument. We therefore vacate Appellant's sentences with respect to Sarah Burger, and remand for resentencing.

¶ 38 Judgment of sentence vacated. Case remanded for resentencing. Jurisdiction relinquished.

¶ 39 Brosky, J.: files a Concurring Opinion.