delivered this concurring opinion,
joined by PRICE and JOHNSON, J.J.Appellant claims the “child capital murder statute” is unconstitutional because it does not require the State to prove that the defendant knew the victim was under the age of six and therefore it does not require proof of any additional “aggravating” circumstance. Appellant argues this provision violates equal protection because other capital murder provisions require that the defendant have knowledge of the aggravating circumstances.
The majority correctly concludes that in assessing appellant’s equal protection *901claim, the “rational basis” test applies. Majority opinion at 3. Thus, the legislature’s classification need only be rationally related to a legitimate governmental purpose. Put another way, we need only be assured “that the classification at issue bears some fair relationship to a legitimate public purpose.” Plyler v. Doe, 457 U.S. 202, 216, 102 S.Ct. 2382, 72 L.Ed.2d 786 (1982).
So what legitimate public purpose is served by classifying the murder of a young child as a capital offense, with no requirement that the defendant have knowledge of the victim’s age, that is not served in the case of the murder of a peace officer or fireman, which require knowledge of the victim’s status? 1 The capital murder classification among these various victims seems, at least in part, to turn upon what it is that renders the victim vulnerable to the offender. Children under six are always vulnerable to the offender. They have virtually no choice about their circumstances; they are entirely at the mercy of anyone who is bigger or who wields some kind of authority. Peace officers and firemen are rendered vulnerable to a criminal offender when they are acting in the lawful discharge of their official duty and the offender has knowledge of their status, and therefore feels threatened by them.2 Different classes of victims have particular vulnerabilities unique to that class. Children are uniquely vulnerable solely by virtue of their status as children. This vulnerability serves as a legitimate basis for the classification of the murder of a child under six a capital offense, without any showing of knowledge of the child’s age on the part of the defendant.
Appellant suggests that without a knowledge requirement, the child-capital murder provision does not require proof of an aggravating element. The victim’s status as a child under the age of six raises what would otherwise be murder to a capital murder. To pass muster under the Eighth Amendment, the aggravating circumstance elevating murder to a capital offense must meet two requirements: “First, the circumstance may not apply to every defendant convicted of murder; it must apply only to a subclass of defendants convicted of murder. [Citation omitted]. Second, the aggravating circumstance must not be unconstitutionally vague.” Tuilaepa v. California, 512 U.S. 967, 971-72, 114 S.Ct. 2630, 129 L.Ed.2d 750 (1994). The child-murder provision meets both tests: those who murder children under six years of age fall within a subclass of murderers in general, and children under six is a clear and definite category. Henderson v. State, 962 S.W.2d 544, 563 (Tex.Crim.App.1997), cert. denied, 525 U.S. 978, 119 S.Ct. 437, 142 L.Ed.2d 357 (1998).
With these comments, I join the majority’s opinion.
. The only other type of capital murder that is dependent upon the victim’s status as the aggravating element is murder of a peace officer or fireman. Tex. Penal Code § 19.03(a)(1).
. It is an offender's knowledge of the officer’s or fireman's status, leading to the offender’s inevitable perception of them as a threat, that renders them vulnerable. A peace officer or fireman who is off-duty is generally not any more vulnerable to a criminal offender than anyone else. When off-duty, they are not placed in circumstances in which they present an apparent threat to a criminal offender.