COOPER, Justice.
On March 15, 2001, Troy Thornsberry and his pregnant wife, Veronica Jane Thornsberry, were en route to Pikeville Methodist Hospital for the anticipated birth of their unborn child when their vehicle was struck by a pickup truck operated by Appellee, Christopher Charles Morris. Mr. Thornsberry was injured in the collision; his wife and unborn child were killed. A post-mortem examination revealed that the child was a viable fetus who would have been born a healthy baby girl had she not sustained a fatal brain injury in the collision.1
A Pike County grand jury indicted Ap-pellee for one count of assault in the first degree, KRS 508.010(l)(b), for causing Mr. Thornsberry’s injuries, and two counts of wanton murder, KRS 507.020(l)(b), for causing the deaths of Mrs. Thornsberry and her unborn child. When the Pike Circuit Court refused to dismiss the charge pertaining to the death of the unborn child, Appellee accepted a plea offer pursuant to which he entered guilty pleas to reduced charges of assault in the second degree, KRS 508.020(l)(c), and manslaughter in the second degree, KRS 507.040(l)(a), with respect to the injury of Mr. Thornsberry and the death of Mrs. Thornsberry, and a conditional guilty plea to manslaughter in the second degree with respect to the death of the unborn child. RCr 6.16; RCr 8.08; RCr. 8.09. He was sentenced to concurrent terms of ten years in prison for each conviction and appealed only the conviction arising from the death of the unborn child.
The Court of Appeals reversed, holding that the common law “born alive” rule, which Hollis v. Commonwealth, Ky., 652 S.W.2d 61 (1988), had applied to the homicide offenses defined in KRS Chapter 507 of the Kentucky Penal Code, precluded a homicide conviction for killing an unborn child. We granted discretionary review to reconsider Hollis.
The Commonwealth presents two arguments: (1) that the “born alive” rule has been superseded by the statutory definition of “human being” in the abortion statutes, i.e., KRS 811.720(6), viz: “‘Human being’ shall mean any member of the species homo sapiens from fertilization until death;” or, in the alternative, (2) that the “born alive” rule is an anachronism that should not be applied when the victim is a viable fetus. Because the rationale for the “born alive” rule no longer exists, we agree that the rule should be discarded. We hold that the felonious killing of a viable fetus can be prosecuted as a homicide under Chapter 507 of our penal code. However, because Due Process precludes retrospective application of that holding, we are required to affirm the result reached by the Court of Appeals.
I. “BORN ALIVE.”
The earliest commentator on the common law of England suggested that the killing of a fetus, or at least a “quickened” fetus, was a homicide.
If there be anyone who strikes a pregnant woman or gives her a poison [656]*656whereby he causes an abortion, if the foetus be already formed or animated, especially if it be animated, he commits homicide.
III Henry de Bracton, The Laws and Customs of England, ii., 4 (circa 1274), as translated from the original Latin into English by Cyril C. Means, Jr., The Law of New York Concerning Abortion and the Status of the Foetus, 1660 — 1968: A Case of Cessation of Constitutionality, 14 N.Y.L.F. 411, 419 (1968). Bracton cited no authority for his proposition2 and it was not followed in two subsequent anonymous cases before the King’s Bench during the reign of Edward III. In the first case, reported in Year Book Michaelmas (Y-B.Mich.), 1 Edw. 3, f. 23, pi. 18 (1327) and dubbed The Twinslayer’s Case by Professor Means, the accused supposedly had beaten a woman who was in the advanced stages of pregnancy with twins. One of the twins died in the womb. The other was born alive but died shortly thereafter, allegedly 'as a result of the beating. The accused was acquitted of killing both twins. Means, The Phoenix of Abortional Freedom, supra note 2, at 337 (providing English translation of original French text). The holding with respect to the twin who was born alive but later died was subsequently rejected by Coke, infra, and by later English courts. Rex v. Senior, 1 Moody 346, 168 Eng. Rep. 1298 (Cr.Cas.Res.1832); Regina v. West, 2 Cox’s Cases in Crim. L. 500 (Nottingham Spring Assizes 1848). See also Jones v. Commonwealth, Ky., 830 S.W.2d 877, 878-79 (1992) (conviction of manslaughter in the second degree affirmed where victim was born alive but subsequently died of injuries inflicted in útero).
The second case rejecting sub silentio Bracton’s proposition was reported by Sir Anthony Fitzherbert in Graunde Abridgement, tit. Corone, f. 268, pi. 263 (1st ed. 1516), f. 255, pi. 263 (3d ed. 1565) (Y.B. Mich., 22 Edw. 3 (1348)), and dubbed The Abortionist’s Case by Professor Means. The accused was charged with killing a child in its mother’s womb but was acquitted partially because “it is difficult to know whether he killed the child or not.” Means, The Phoenix of Abortional Freedom, supra note 2, at 339. Thus, “ ‘[i]f the child be destroied in the mothers belly, the destroier is no manslayer, nor Felone.’” Id. at 342 (quoting William Lambarde, Eirenarcha, or of The Office of the Justices of the Peace 217-18 (2d ed. 1582)). The reason for the rule was “non constat [it could not be established], whether the child were living at the time of the batterie or not, or if the batterie was the cause of death.” Sims’s Case, Gouldsborough 176, pi. 110, 75 Eng. Rep. 1075 (K.B.1601).
Coke’s now-famous enunciation of the “born alive” rule is as follows:
If a woman be quick with childe, and by a Potion or otherwise killeth it in her wombe; or if a man beat her, whereby the childe dieth in her body, and she is delivered of a dead childe, this is a great misprision, and no murder: but if the childe be born alive, and dieth of the [657]*657Potion, battery, or other cause, this is murder: for in law it is accounted a reasonable creature, in rerum natura, when it is born alive.
Sir Edward Coke, Third Institute 50-51 (1644).3 The rule was repeated in later British treatises. 1 William Hawkins, Treatise of the Pleas of the Crown, ch. 31, § 16, at 80 (1716); Matthew Hale, History of the Pleas of the Crown 483 (1736); 1 William Blackstone, Commentaries 129-30 (1765).
The “born alive” rule is reported to have first been applied in the United States in Commonwealth v. McKee, 1 Add. 1 (Pa. 1791). See Clarke D. Forsythe, Homicide of the Unborn Child: The Bom Alive Rule and Other Legal Anachronisms, 21 Val. U.L.Rev. 563, 598 (1987). Prior to legislative reform, it was almost universally applied. See Commonwealth v. Booth, 564 Pa. 228, 766 A.2d 843, 849 (2001), and cases cited therein. The rule continued to be one of necessity. As late as the nineteenth century, prior to quickening, “it was virtually impossible for either the woman, a midwife, or a physician to confidently know that the woman was pregnant, or, it follows, that the child in útero was alive.” Forsythe, supra, at 573. Hence, there was no evidence of life until quickening. Id. Even quickening did not constitute proof that the fetus was alive at any particular moment thereafter. The health of a fetus could not be determined until after its birth. Id. at 575. “As a result, live birth was required to prove that the unborn child was alive and that the material acts were the proximate cause of death, because it could not otherwise be established if the child was alive in the womb at the time of the material acts.” Id.
The “born alive” rule first entered Kentucky’s jurisprudence in the pre-penal code case of Jackson v. Commonwealth, 265 Ky. 295, 96 S.W.2d 1014 (1936).
“[I]n order to establish the corpus de-licti, in a case of infanticide, it must also be established that the child was born alive. In the absence of proof that the child had ever breathed or was alive at birth a conviction can not be sustained. It is necessary for the Commonwealth to prove affirmatively, not only that the child had breathed, because that might occur during birth, but that it had had a complete and separate existence of its own after birth. Being born means that the whole body is brought into the world, and it is not sufficient that the child breathes in the progress of the birth. But if a child is fully brought forth from the body of its mother, and is killed while still connected by the umbilical cord, it is murder. When the evidence that the child was born alive is susceptible of doubt, a conviction can not be sustained.”
Id., 96 S.W.2d at 1014-15 (emphasis added) (quoting James M. Roberson, New Kentucky Criminal Law and Procedure § 425 (2d ed.1927)). Jackson, a murder case, held that the Commonwealth had established the corpus delicti through “[tjhe testimony of the physicians, together with that of the accused .... ” Id. at 1016. Thus, as first applied in Kentucky, the “born alive” rule pertained to the sufficiency of the evidence needed to support a conviction of homicide, not the interpretation of a statute. See also Forsythe, supra, at 586 (The “born alive” rule “is recognized to be an evidentiary principle that was required by the state of medical science of the day.”).
[658]*658II. HOLLIS.
When Jackson was decided, murder was a common law offense and only the penalty was prescribed by statute. KS § 1149 (repealed 1942 Ky. Acts, ch. 208, § 2). Involuntary manslaughter (which now includes the offense of manslaughter in the second degree) was also a common law offense 4 but had no statutorily prescribed penalty, so was thus a misdemeanor punishable only by fíne and/or confinement in the county jail. KS § 1127 (repealed 1942 Ky. Acts, ch. 208, § 2); Cottrell v. Commonwealth, 271 Ky. 52, 111 S.W.2d 445, 448 (1937); Spriggs v. Commonwealth, 113 Ky. 724, 68 S.W. 1087, 1088 (1902). Upon the adoption of the Kentucky Penal Code, effective January 1, 1975, common law offenses were abolished and all offenses, including homicides, were thereafter to be defined by statute. KRS 500.020(1).
KRS 507.040 provides, inter alia::
(1) A person is guilty of manslaughter in the second degree when he wantonly causes the death of another person including, but not limited to, situations where the death results from the person’s:
(a) Operation of a motor vehicle ....
(Emphasis added.) Similarly, the murder statute, KRS 507.020, refers to causing the death of “another person.” KRS 500.080 has always provided that, “[a]s used in the Kentucky Penal Code,” “ ‘person’ means a human being _” KRS 500.080(12). Likewise, KRS 507.010, titled “Definitions,” has always provided:
A person is guilty of criminal homicide when he causes the death of another human being under circumstances which constitute murder, manslaughter in the first degree, manslaughter in the second degree, or reckless homicide.
(Emphasis added.)
Hollis v. Commonwealth, supra, like Jackson, was a murder case that, like the case sub judice, involved the killing of a proven viable fetus. Because the fetus was killed before it was “born alive,” Hollis held that a homicide had not been committed. Id. at 64-65. In interpreting KRS 507.020,5 the plurality opinion in Hollis first inaccurately reported that “[t]he statute makes no effort to define the word ‘person Id. at 63. But see KRS 500.080(12) which, by its very language, applies to all penal code offenses, and KRS 507.010. The opinion then reasoned that in the absence of a statutory definition, the General Assembly would be presumed to have intended to retain the common law definition of “person,” which the opinion then concluded was the “born alive” rule adopted in Jackson. Hollis, supra, at 63. The concurring opinion in Hollis rejected this flawed statutory construction but nevertheless concluded that the holding in Jackson had survived the abolition of common law homicide offenses.
Jackson, supra, had not been overruled when the act was committed by Hollis. I believe he was entitled to rely upon the decisions of this court which had not been repudiated.
Id. at 65 (Vance, J., concurring).
We do not know why the Hollis plurality chose to ignore the existence of KRS 500.080(12) and KRS 507.010, both of which define “person” as “a human being,” [659]*659and instead employed a common law evi-dentiary requirement as the definition of “person.” Remember, Jackson, supra, had not applied the “born alive” rule as a definition but as the proof required to establish the corpus delicti of the common law offense of murder. Id., 96 S.W.2d at 1014. Perhaps the Hollis plurality had its eye on the definition of “human being” in the abortion statutes, supra. Although the effective date of KRS 311.720(6) was April 7, 1982 (1982 Ky. Acts, ch. 342, § 2), and Hollis was rendered on March 30, 1983, the offense in Hollis occurred prior to the enactment of the abortion statutes, thus precluding the application of KRS 311.720(6) to that case. See the discussion of the Ex Post Facto Clause in Part V, infra. However, the Hollis plurality may have concluded that by construing “person” instead of “human being,” it could avoid a potential future argument, such as the one advanced here by the Commonwealth, that KRS 311.720(6) abrogated the common law interpretation applied in Hollis.
By construing “person” instead of “human being,” the Hollis plurality also may have intended to deflect attention away from the fact that the drafters of the Kentucky Penal Code did not adopt the definition of “human being” espoused in the Model Penal Code (MPC) i.e., “a person who has been born and is alive.” MPC § 210.0(1). As noted by the Hollis plurality, 652 S.W.2d at 63, the MPC influenced the drafters of the homicide provisions of the Kentucky Penal Code. See KRS 507.020-.040 (1974 Commentary).6 See generally Robert G. Lawson, Criminal Law Revision in Kentucky: Part I— Homicide and Assault, 58 Ky. L.J. 242 (1969-70). Nevertheless, the drafters did not adopt the MPC’s definition of “human being” which, as suggested by the dissent in Hollis, provides some evidence of a legislative intent not to incorporate the “born alive” rule into our penal code. Id. at 67 (Wintersheimer, J., dissenting). Remarkably, the Hollis plurality cited the Comment to the MPC’s definition of “human being” for the proposition that the drafters of the Kentucky Penal Code did intend to retain the “born alive” rule. Id. at 63 (quoting MPC § 210.1 cmt. 4(c)).
III. VIABLE FETUS.
Medical science has now advanced to the stage that the viability, health, and cause of a fetus’s death can be determined. See Mary Lynn Kime, Hughes v. State: The “Bom Alive” Rule Dies a Timely Death, 30 Tulsa L.J. 539, 543 (1995); Stephanie R. McCavitt, Note, The “Bom Alive” Rule: A Proposed Change to the New York Law Based on Modem Medical Technology, 36 N.Y.L. Sch. L.Rev. 609, 636-37 (1991). Thus, the rationale for the “born alive” rule no longer exists. Hughes v. State, 868 P.2d 730, 732 (Okla.Crim.App.1994). Specifically, there is no need for it in the case sub judice because the post-mortem examination clearly proved that the unborn victim was a viable fetus who would have been born alive and completely normal except for the fatal brain injury sustained in the vehicular collision caused by Appel-lee. To quote Justice Holmes:
It is revolting to have no better reason for a rule of law than that so it was laid down in the time of Henry IV. It is still more revolting if the grounds upon which it was laid down have vanished long since, and the rule simply persists from blind imitation of the past.
[660]*660Oliver Wendell Holmes, The Path of the Law, 10 Harv. L.Rev. 457, 469 (1896-97).
The more enlightened cases have departed from the “born alive” rule in favor of recognizing that a viable fetus can be the victim of a homicide. See, e.g., Commonwealth v. Cass, 892 Mass. 799, 467 N.E.2d 1824, 1325-26 (1984) (viable fetus is a “person” under a vehicular homicide statute criminalizing causing the death of “another person”); Hughes v. State, supra, at 731 (viable fetus is a “human being” under statute defining homicide as the killing of a “human being”); State v. Home, 282 S.C. 444, 319 S.E.2d 703, 704 (1984) (viable fetus is a “person” within statute defining murder as the killing of “any person”). Viability was recognized in Roe v. Wade, 410 U.S. 113, 93 S.Ct. 705, 35 L.Ed.2d 147 (1973), as the “compelling” point at which “the fetus then presumably has the capability of meaningful life outside the mother’s womb,” and the earliest time at which a state may proscribe consensual abortions. Id. at 163-64, 93 S.Ct. at 732. It is also the point at which the killing of an unborn child gives rise to a civil cause of action for wrongful death on behalf of the unborn child’s estate. KRS 411.130.
The most cogent reason, we believe, for holding that a viable unborn child is an entity within the meaning of the general word “person” is because, biologically speaking, such a child is, in fact, a presently existing person, a living human being. It should be pointed out that there is a definite medical distinction between the term “embryo” and the phrase “viable fetus.” The embryo is the fetus in its earliest stages of development, but the expression “viable fetus” means the child has reached such a state of development that it can presently live outside the female body as well as within it. A fetus generally becomes a viable child between the sixth and seventh month of its existence, although there are instances of younger infants being born and surviving.
Mitchell v. Couch, Ky., 285 S.W.2d 901,. 905 (1955) (citing William J. Cason, May Parents Maintain an Action for the Wrongful Death of an Unborn Child in Missouri? The Case for the Right of Action, 15 Mo. L.Rev. 211, 218 (June 1950)). See also Rice v. Rizk, Ky., 453 S.W.2d 732, 735 (1970). Whether a fetus was viable when killed is just as provable by competent evidence as whether a child was born alive or stillborn. See Jackson, 96 S.W.2d at 1016 (“The testimony of the physicians together with that of the accused, establishes beyond cavil, doubt, or question” that the child was born alive.).
It is inherently illogical to recognize a viable fetus as a human being whose estate can sue for wrongful death and who cannot be consensually aborted except to preserve the life or health of the mother, but not as a human being whose life can be nonconsensually terminated without criminal consequences. Thus, we overrule Hollis and hold that a viable fetus is a “human being” for purposes of KRS 500.080(12) and the KRS Chapter 507 homicide statutes.
IV. THE ABORTION STATUTES.
The Commonwealth argues that the penal code’s definition of “person” as “a human being” ipso facto requires application of the definition of “human being” in KRS 311:720(6) to the penal code. As noted supra, that statute defines “human being” as “any member of the species homo- sa-piens from fertilization until death.” However, while the introductory sentence in KRS 311.720 purports to apply the definitions enumerated therein to “KRS 311.710 to 311.820, and laws of the Commonwealth unless the context otherwise requires ” [661]*661(emphasis added), the definition of “human being” was added to KRS 311.720 by an Act entitled, “AN ACT relating to abortion.” 1982 Ky. Acts, ch. 342, § 2. Section 51 of our Constitution provides that “[n]o law enacted by the General Assembly shall relate to more than one subject, and that shall be expressed in the title .... ” (Emphasis added.) Thus, the definition of “human being” set forth in KRS 311.720(6) cannot constitutionally be applied to the homicide provisions of the penal code. Edwards v. Land, Ky.App., 851 S.W.2d 484, 487 (1992) (if a portion of the Act falls within the scope of the title and another portion falls outside the scope of the title, the portion falling outside may be omitted), overruled on other grounds by O’Bryan v. Hedgespeth, Ky., 892 S.W.2d 571, 578 (1995).7
Y. THE FETAL HOMICIDE STATUTE.
House Bill 108, 2004 Gen. Assem., Reg. Sess. (Ky.2004), effective February 20, 2004 (nine days after the oral argument in this case), which became KRS Chapter 507A, created the new offense of “fetal homicide.” The bill defines “unborn child” as “a member of the species homo sapiens in útero from conception onward, without regard to age, health, or condition of dependency.” H.B. 108 § 1(c). The Ex Post Facto Clauses of both the United States and Kentucky Constitutions preclude retrospective application of this statute to Appellee’s conduct with respect to the unborn child in this case. U.S. Const., art. I, § 10, cl. 1; Ky. Const. § 19(2). However, we are invited to use this case as a vehicle to prospectively adopt that definition via common law. (See Wintersheimer, J., concurring, post.) Of course, KRS 507.040, the statute we now construe, refers not to an “unborn child,” but to a “person,” further defined as “a human being.” Since the human being that is the subject of this appeal was a viable fetus, it is unnecessary to address in this opinion whether killing a nonviable fetus would violate KRS 507.040. Presumably, future homicides of nonviable fetuses will be prosecuted under KRS Chapter 507A.
Furthermore, to prematurely approve the definition in H.B. 108 would preempt a potential “void for vagueness” challenge to the statute, essentially declaring it constitutional without benefit of either briefs or arguments.8 It might also tempt an overly zealous prosecutor to cite such a holding in an attempt to apply the KRS Chapter 507 homicide statutes to a consensual abortion of a nonviable fetus, or to seek the death penalty for the double murder of a pregnant woman and her nonviable fetus, applications expressly precluded in the new fetal homicide law. H.B. 108, supra, at §§ 1(2), (3); 6.
VI. THE “REENACTMENT DOCTRINE.”
Justice Keller correctly notes the validity of the “reenactment doctrine” in his concurring opinion, post. ‘“It is a generally recognized rule of statutory construction that when a statute has been [662]*662construed by a court of last resort and the statute is subsequently reenacted, the Legislature may be regarded as adopting such construction.’ ” Hughes v. Commonwealth, Ky., 87 S.W.3d 850, 855-56 (2002) (quoting Commonwealth v. Trousdale, 297 Ky. 724, 181 S.W.2d 254, 256 (1944)). However, the so-called “reenactment doctrine” does not require continued application of the “born alive” rule to our homicide statutes.
First, the lead opinion in Hollis was a plurality opinion joined by only three members of the Court. Two members concurred in result only and the remaining two members dissented. The two concurring members based their concurrence on the premise that Jackson v. Commonwealth, supra, “had not been overruled when the act was committed [and the defendant] was entitled to rely upon the decisions of this court which had not been repudiated.” Hollis, 652 S.W.2d at 65 (Vance, J., concurring). Obviously, the two separately concurring members concluded that the adoption of the penal code had not abrogated the common law holding in Jackson that proof of the corpus delicti of a homicide required proof that the victim was “born alive.” They did not join the plurality opinion’s analysis of legislative intent with respect to the definition of “person” in KRS 507.020. Id. (“I do not believe it is necessary or proper to extend the opinion of this court to the other issues discussed in the [plurality] opinion, and for that reason I concur in the result only.”). Thus, the Hollis plurality’s construction of the word “person” in KRS 507.020 was not a holding of the Court to which the legislature would be deemed to have implicitly acquiesced when it subsequently amended and/or reenacted KRS 507.020 and KRS 507.040 without redefining the word “person.”
Of course, our subsequent decision in Jones v. Commonwealth, supra, was a majority opinion. However, the holding in Jones was that a child who was born alive and subsequently died from injuries inflicted in útero was a “person” within the meaning of KRS 507.040. 830 S.W.2d at 878-79. That holding is not inconsistent with our holding in this case.
Furthermore, since the General Assembly had already twice defined “person” as “a human being” for purposes of the penal code and the homicide statutes in KRS 500.080(12) and KRS 507.010, and the Hollis plurality did not attempt to construe either of those statutes, the Hollis plurality opinion arguably did not affect the statutory definition of “person” in any respect. Compare Blauner’s Inc. v. City of Phila., 198 A. 889, 893, 330 Pa. 340 (1938) (common law definitions irrelevant where statute contains its own definition); Kohn v. City of Phila., 151 Pa.Super. 635, 30 A.2d 672, 675 (1943) (“None of these cases [reciting common law definitions of ‘sale’] has any relevancy-here where ‘sale’ is defined by the ordinance.”). Thus, the “reenactment doctrine” does not affect our decision to overrule Hollis.
VII. “FAIR WARNING.”
Just as the Ex Post Facto Clause precludes retrospective application of new legislation, e.g., H.B. 108, to conduct that was not illegal when committed, the retrospective application by a court of an unforeseeable .change in the common law or in the interpretation of a statute to the detriment of a criminal defendant violates the “fair warning” requirement of the Due Process Clause. U.S. Const, amends. V, XIV § 1.
A “fair warning” violation occurs “[w]hen a[n] ... unforeseeable state-court [sic] construction of a criminal statute is applied retroactively to subject [663]*663a person to criminal liability for past conduct, the effect [being] to deprive him of due process of law in the sense of fair warning that his contemplated conduct constitutes a crime.” Bouie v. City of Columbia, 378 U.S. 347, 854-55, 84 S.Ct. 1697, 1703, 12 L.Ed.2d 894 (1964).... See also Gall v. Parker, 231 F.3d 265, 305-06 (6th Cir.2000) (detrimental application of new judicial interpretation of extreme emotional disturbance defense to conduct occurring when more favorable interpretation was in effect violated “fair warning” requirement). The “fair warning” requirement also applies to changes in common law principles that are “ ‘unexpected and indefensible by reference to the law which had been expressed prior to the conduct in issue.’” Rogers v. Tennessee, 532 U.S. 451, 460-62, 121 S.Ct. 1693, 16991700, 149 L.Ed.2d 697 (2001) (state court’s abolishment of common law “year and a day” rule did not violate “fair warning” requirement) (quoting Bouie, supra, at 354, 84 S.Ct. at 1697).
Walker v. Commonwealth, Ky., 127 S.W.3d 596, 603 (2004).
Thus, our decision to overrule Hollis and criminalize the killing of a viable fetus cannot be applied retrospectively to Appel-lee’s conduct.9 Accordingly, we affirm the result reached by the Court of Appeals, but for a different reason than expressed in its opinion.
LAMBERT, C.J.; GRAVES, and JOHNSTONE, JJ., concur.
KELLER, J., concurs by separate opinion, with STUMBO, J., joining that concurring opinion.
WINTERSHEIMER, J., concurs by separate opinion.