OPINION
NIEMEYER, Circuit Judge:Section 19.2-310.2 of the Virginia Code, effective July 1, 1990, requires convicted felons to submit blood samples for DNA analysis “to determine identification characteristics specific to the person” and provides for the creation of a data bank of the information for future law enforcement purposes. Six inmates have challenged the statute’s constitutionality, contending that it authorizes the involuntary extraction of blood in violation of the Fourth Amendment prohibition against unreasonable searches' and seizures. They also contend the statute violates the Ex Post Facto Clause principally because it defers until receipt of a blood sample the release of inmates who committed crimes before the statute’s effective date.
On cross-motions for summary judgment, the district court upheld the constitutionality of the Virginia statute against both attacks. In the inmates’ appeal, which presents a case of first impression for us, we affirm except to the limited extent that the statute purports to authorize a modification of mandatory parole conditions for prisoners incarcerated on July 1, 1990.
I
Deoxyribonucleic acid (DNA) is a complex molecule which is found in the nuclei of human cells and carries a person’s genetic information. A molecule of DNA. is comprised of two nucleotide strands coiled around each other and connected by rungs, like a twisted ladder. The strands and rungs link thousands of small components which exist in a number of biochemical variations and are arranged differently for every individual except for identical twins. *304At present, the white blood cells are the most commonly used source for the extraction and analysis of human DNA.
Improved scientific technology has prompted efforts to use the individuality of a person’s DNA in the context of criminal law enforcement. The method for “typing” DNA known as the “DNAPrint” test is favored by the Commonwealth of Virginia and is currently being used elsewhere with varying degrees of success for criminal identification. This scientific process for analyzing DNA produces a “print” which contains a pattern of bands that is supposed to be unique to a particular person’s DNA. One potential use for this print would be to compare it with an analysis of DNA material found at a crime scene as a means of identifying or exonerating a particular criminal suspect. Commonwealth officials claim that material susceptible to DNA analysis, including blood, skin tissue, hair follicles, and semen, may be found at thirty per cent of all crime scenes. Another application might involve use of the print for identifying a criminal suspect who has attempted to alter and conceal his or her identity and who had previously provided a sample to a DNA data bank.
In 1990, the Commonwealth of Virginia by statute established a DNA data bank and procedures for the collection, analysis, and exchange of DNA information for the purpose of criminal law enforcement. See Va.Code Ann. §§ 19.2-310.2 through 19.2-310.7 (Michie 1990). Commonwealth officials say that the program attempts to address the problem of felony recidivism in Virginia by identifying and increasing the likelihood of convicting repeat offenders and by deterring those who might otherwise commit a second felony. According to a study of violent felons convicted in Virginia between 1985 and 1987, 36.4% had at least one prior conviction for a felony. Only 26% had no prior criminal record and just over 19% had previously been convicted of nonviolent felonies. A United States Department of Justice survey of more than half of those persons released from the prisons of eleven states in 1983 revealed that an estimated 62.5% were arrested again for a felony or serious misdemeanor within three years after release.
The 1990 Virginia law provides that incarcerated felons shall provide the Commonwealth with a blood sample for DNA analysis and storage. Va.Code Ann. § 19.2-310.2. The provision applies to (1) all persons convicted of a felony on or after July 1, 1990; (2) all felons incarcerated as of that date; and (3) all sex offenders convicted under §§ 18.2-61 through 18.2-68 of the Virginia Code, and incarcerated on July 1, 1989.1 The law authorizes the release of DNA information to “federal, state and local law-enforcement officers upon request made in furtherance of an official investigation of any criminal offense,” see Va.Code Ann. § 19.2-310.5, but also establishes as a crime the unauthorized dissemination or use of information from the data bank, see Va.Code Ann. § 19.2-310.6. The collection of DNA samples is assigned to the Virginia Department of Corrections and the tasks associated with the DNA analysis and maintenance of the data bank are to be conducted by the Virginia Bureau of Forensic Science.
In implementing the program, the Department of Corrections established procedures by which blood samples would be drawn from those inmates falling within the scope of § 19.2-310.2. With regard to felons entering state correctional facilities on or after July 1, 1990, the department’s guidelines require the chief nurse at reception and classification centers to “cause an additional sterile sample of blood to be drawn at the time routine blood samples are taken for intake physicals.” In addition, the department requires “[ejvery felon who is in custody on or after July 1, 1990, and has not previously provided a sample of blood for DNA testing purposes, [to] provide a blood sample prior to the individual’s discretionary parole eligibility date (or thirty days prior to the mandatory *305parole date if the discretionary date has passed).”
On October 9, 1990, six inmates at the Tazewell Correctional Unit Number 31 challenged the implementation of the DNA program in an action filed pursuant to 42 U.S.C. § 1983 against Edward Murray, the Director of the Virginia Department of Corrections and Paul Ferrara, the Director of the Bureau of Forensic Science. The inmates requested a temporary restraining order and a preliminary injunction, as well as class certification for those individuals who have been or will be convicted of a felony under the laws of Virginia and who will be subjected to blood testing for DNA analysis. The inmates principally complained that Virginia’s program is unconstitutional on three grounds: 1) the collection and analysis of blood samples violates the inmates’ Fourth Amendment rights; 2) the retroactive imposition of the blood test requirement as a condition of release, including release under mandatory parole, violates the Constitution’s Ex Post Facto Clause; and 3) the imposition of a blood-test condition on the inmates’ release date interferes with a vested liberty interest and violates the Fourteenth Amendment’s Due Process Clause. The district court denied the requests for preliminary relief, but on October 26, 1990, certified a plaintiff class.
On March 4, 1991, on cross-motions for summary judgment the court decided the Fourth Amendment question in favor of the Virginia officials. 763 F.Supp. 842. The court held that blood testing of incarcerated felons for the purpose of future identification falls within the Supreme Court’s “special needs” exception to the Fourth Amendment’s warrant requirement. Balancing the state interest in establishing the DNA bank against the intrusion upon the inmates’ privacy interest, the court determined that the taking of blood samples under these circumstances is reasonable. The district court further held that the blood test requirement does not violate the Ex Post Facto Clause, because it is neither a punitive measure nor a requirement of parole eligibility, and the inmates’ parole is not affected. Rather, it concluded, release from prison is simply deferred until the blood-sample is provided. Finally, the district court concluded that an inmate’s release date does implicate a protected liberty interest and thus a “prisoner must be given some process before he is héld beyond his established parole release date.” Neither party appealed the district court’s decision with respect to the Due Process issue.
II
The principal argument advanced by the inmates is grounded on the contention that Virginia’s blood testing program violates the -inmates’ Fourth Amendment rights against unreasonable searches and seizures by authorizing the search of their bodies in the absence of any individualized suspicion. They argue that the general purpose of enforcing the law by improving methods of identification is not sufficient to justify testing an entire class of people merely because the recidivism rate is higher for them. They note that several classifications of persons, for example, those affected by mental disease or environmental factors, who have never before been convicted of a crime, might statistically be equally likely to commit future crimes. They contend that the district court’s ruling sustaining the Virginia program is “the first instance ... that a pure law enforcement search has ever been sustained in the absence of any individualized suspicion.”
The Commonwealth of Virginia observes that if individualized suspicion must exist before any felon can be required to submit to a blood test, any meaningful DNA identification bank will be impossible. The very idea of establishing a data bank refutes the possibility of establishing individualized suspicion because the collection of the blood samples is designed to solve future cases for which no present suspicion can exist. It argues that the special needs of the government warrant application of the balancing test identified in Skinner v. Railway Labor Executives’ Ass’n, 489 U.S. 602, 109 S.Ct. 1402, 103 L.Ed.2d 639 (1989), and National Treasury Employees Union v. Von Raab, 489 U.S. 656, 109 S.Ct. 1384, 103 L.Ed.2d 685 (1989). When considering the minimal level of intrusion, the Common*306wealth argues, demonstrably higher rates of recidivism among felons and the improved methods of identification provided by DNA analysis justify the search. They refer to studies, including one which concluded:
Of the 108,580 persons released from prisons in 11 states in 1983, representing more than half of all released State prisoners that year, an estimated 62.5% were arrested for a felony or serious misdemeanor within 3 years.... Before their release from prison, the prisoners had been arrested and charged with an average of more than 12 offenses each; nearly two-thirds had been arrested at least once in the past for a violent offense; and two-thirds had previously been in jail or prison_ An estimated 22.7% of all prisoners were rearrested for a violent offense within 3 years of their release.
Allen J. Beck & Bernard E. Shipley, U.S. Dep’t of Justice Recidivism of Prisoners Released in 1983 1 (1989). In Virginia the statistics are not significantly different. See Department of Criminal Justice Services, Commonwealth of Virginia Violent Crime in Virginia 30-31 (May 1989).
It appears to be established, at least with respect to free persons, that the bodily intrusion resulting from taking a blood sample constitutes a search within the scope of the Fourth Amendment. See Skinner, 489 U.S. at 616, 109 S.Ct. at 1412; Schmerber v. California, 384 U.S. 757, 86 S.Ct. 1826, 16 L.Ed.2d 908 (1966). And in the view of the inmates, all governmental searches conducted in the context of criminal law enforcement require individualized suspicion to satisfy the Fourth Amendment’s requirement of reasonableness. See, e.g., Terry v. Ohio, 392 U.S. 1, 20-21, 88 S.Ct. 1868, 1879-80, 20 L.Ed.2d 889 (1968).
We have not been made aware of any case, however, establishing a per se Fourth Amendment requirement of probable cause, or even a lesser degree of individualized suspicion, when government officials conduct a limited search for the purpose of ascertaining and recording the identity of a person who is lawfully confined to prison. This is not surprising when we consider that probable cause had already supplied the basis for bringing the person within the criminal justice system. With the person’s loss of liberty upon arrest comes the loss of at least some, if not all, rights to personal privacy otherwise protected by the Fourth Amendment. Thus, persons lawfully arrested on probable cause and detained, lose a right of privacy.,/ from routine searches of the cavities of their bodies and their jail cells, see Bell v. Wolfish, 441 U.S. 520, 559-60, 99 S.Ct. 1861, 1884-85, 60 L.Ed.2d 447 (1979), as do convicted felons, see Hudson v. Palmer, 468 U.S. 517, 530, 104 S.Ct. 3194, 3202, 82 L.Ed.2d 393 (1984). Even probationers lose the protection of the Fourth Amendment with respect to their right to privacy against searches of their homes pursuant to an established program to ensure rehabilitation and security. See Griffin v. Wisconsin, 483 U.S. 868, 880, 107 S.Ct. 3164, 3172, 97 L.Ed.2d 709 (1987).
Similarly, when a suspect is arrested upon probable cause, his identification becomes a matter of legitimate state interest and he can hardly claim privacy in it. We accept this proposition because the identification of suspects is relevant not only to solving .the crime for which the suspect is arrested, but also for maintaining a permanent record to solve other past and future crimes. This becomes readily apparent when we consider the universal approbation of “booking” procedures that are followed for every suspect arrested for a felony, whether or not the proof of a particular suspect’s crime will involve the use of fingerprint identification. Thus a tax evader is fingerprinted just the same as is a burglar. While we do not accept even this small level of intrusion for free persons without Fourth Amendment constraint, see Davis v. Mississippi, 394 U.S. 721, 727, 89 S.Ct. 1394, 1397, 22 L.Ed.2d 676 (1969), the same protections do not hold true for those lawfully confined to the custody of the state. As with fingerprinting, therefore, we find that the Fourth Amendment does not require an additional finding of individualized suspicion before blood can *307be taken from incarcerated felons for the purpose of identifying them.2
In the absence of a requirement for individualized suspicion, assuming that the Fourth Amendment continues to apply to lawfully confined prisoners, we must nevertheless determine the reasonableness of any search. 'We recognize that the search effected by the taking of blood samples may be considered a greater intrusion than fingerprinting. Yet blood tests are commonplace, see Breithaupt v. Abram, 352 U.S. 432, 436, 77 S.Ct. 408, 410, 1 L.Ed.2d 448 (1957), and the intrusion occasioned by them is “not significant.” See Skinner, 489 U.S. at 625, 109 S.Ct. at 1417. The procedure “ ‘involves virtually no risk,, trauma, or pain.’ ” Id. (quoting Schmerber, 384 U.S. at 771, 86 S.Ct. at 1836). In Skinner, the Supreme Court upheld a program which required mandatory blood testing of an entire class of railway employees, albeit not for law enforcement purposes. Skinner 489 U.S. at 634, 109 S.Ct. at 1422 (upholding drug and alcohol tests for safety reasons). In a similar vein, mandatory blood testing of all prisoners to detect the presence of the Human Immunodeficiency Virus, which causes Acquired Immune Deficiency Syndrome (AIDS), has been justified by the governmental interests in controlling AIDS in prison. See Dunn v. White, 880 F.2d 1188, 1196-97 (10th Cir.1989), cert. denied, 493 U.S. 1059, 110 S.Ct. 871, 107 L.Ed.2d 954 (1990). These decisions instruct that blood testing can be reasonable under the Fourth Amendment, even with respect to free persons, where the slight intrusion is outweighed by the governmental interest advanced by the intrusion. See also Von Raab, 489 U.S. at 679, 109 S.Ct. at 1397; Wolfish, 441 U.S. at 560, 99 S.Ct. at 1885; Hudson, 468 U.S. at 529-30, 104 S.Ct. at 3201-02.
Against the minor intrusion, therefore, we weigh the government’s interest in preserving a permanent identification record of convicted felons for resolving past and future crimes. It is a well recognized aspect of criminal conduct that the perpetrator will take unusual steps to conceal not only his conduct, but also his identity. Disguises used while committing a crime may be supplemented or replaced by changed names, and even changed physical features. Traditional methods of identification by photographs, historical records, and fingerprints often prove inadequate. The DNA, however, is claimed to be unique to each individual and cannot,, within current scientific knowledge, be altered. The individuality of the DNA provides a dramatic new tool for the law enforcement effort to match suspects and criminal conduct. Even a suspect with altered physical features cannot escape the match that his DNA might make with a sample contained in a DNA bank, or left at the scene of a crime within samples of blood, skin, semen or hair follicles. The governmental justification for this form of identification, therefore, relies on no argument different in kind from that traditionally advanced for taking fingerprints and photographs, but with additional force because of the potentially greater precision of DNA sampling and matching methods.
Thus, in the case of convicted felons who are in custody of the Commonwealth, we find that the minor intrusion caused by the taking of a blood sample is outweighed by Virginia’s interest, as stated in the statute, in determining inmates’ “identification characteristics specific to the person” for improved law enforcement. See Va.Code Ann. § 19.2-310.2. .
*308The inmates argue that the usefulness of DNA as an identification technique is largely limited to violent crimes, based upon the unlikelihood of recovering from the scene of a nonviolent crime a DNA sample from the perpetrator that is sufficient for comparison with the suspect’s DNA. According to statistics presented by the inmates, there is only a remote possibility that a nonviolent offender will commit a future violent crime which will produce sufficient DNA for an identification match. These statistics indicate that 97% of the cases in which DNA evidence was used to link a defendant with a crime involved murder or rape, and further, less than 1% of all nonviolent offenders are later arrested on murder or rape charges. They contend therefore that the DNA program cannot be justified with respect to the testing of nonviolent felons.
These numbers persuasively demonstrate, given the DNA technology that is currently available, that Virginia’s interest in DNA testing is significantly more compelling with regard to those felons convicted of violent crimes than those not. However, we note that the fact that fingerprints are not found at a particular crime scene does not negate the Commonwealth’s interest in fingerprinting the criminal suspect when caught. There may be uses for DNA technology other than merely verifying a suspect’s presence at the scene of a crime. As we have noted, a DNA print might be used to identify a criminal suspect who has attempted to alter or conceal his or her identity. Moreover, if DNA technology becomes more common (and particularly if it is established as a reliable and judicially accepted identification tool), then it is likely that law enforcement officials will become more aware of the technology and thus more likely to make use of the DNA clues that are left as a result of crimes other than murder or rape. The effectiveness of the Commonwealth’s plan, in terms of percentage, need not be high where the objective is significant and the privacy intrusion limited. See Michigan Dept. of State Police v. Sitz, 496 U.S. 444, 110 S.Ct. 2481, 2487, 110 L.Ed.2d 412 (1990) (validating state use of roadblock to discover drunk drivers despite resulting arrest rate of only 1.5%); Wolfish, 441 U.S. at 559, 99 S.Ct. at 1884 (validating body cavity search of pretrial detainees despite only one instance in which an inmate was discovered attempting to smuggle contraband).
It is not for us to weigh the advantages of one method of identification over another which is selected by the Commonwealth. While greater utility for use of DNA data can be supposed when the future crime is one of violence and those crimes can statistically be related more directly to inmates now incarcerated for crimes of violence, the utility of more exact identification in all cases still justifies the minor intrusion. We therefore agree with the district court’s conclusion that § 19.2-310.2 does not violate the Fourth Amendment as applied by the Fourteenth Amendment to the Commonwealth of Virginia.
Ill
The inmates next argue that Virginia’s statute violates the constitutional prohibition against ex post facto laws, principally because an enforcement mechanism of Virginia’s DNA blood testing requirement appears retroactively to authorize an extension of the inmates’ sentences into their period of mandatory parole. As part of its plan to establish the DNA bank, which was enacted in April 1990, Virginia requires:
After July 1, 1990, the blood sample shall be taken [from incarcerated felons] prior to release from custody.
Notwithstanding the provisions of 53.1-159, [the mandatory release on parole requirement], any person convicted of a felony who is in custody after July 1, 1990, shall provide a blood sample prior to his release.
Va.Code Ann. § 19.2-310.2 (emphasis added). Section 53.1-159, which was applicable to the sentences of the inmates incarcerated at the time § 19.2-310.2 was enacted, provides:
Every person who is sentenced and committed under the laws of the Com*309monwealth to the Department of Corrections ... shall be released on parole by the Virginia Parole Board six months prior to his date of final discharge,
(emphasis added). This mandatory release provision allows only one exception: an inmate’s release may be delayed up to six months, if new information is given to the Parole Board within thirty days of the scheduled release date “which gives the Board reasonable cause to believe that the release poses a clear and present danger to the life or physical safety of any person.” Va.Code Ann. § 53.1-159. The inmates contend that retroactively authorizing prison officials to lengthen their sentences for failure to give blood samples constitutes an ex post facto punishment.
While the Ex Post Facto Clause provides simply and without explanation, “No State shall ... pass any ... ex post facto Law,” U.S. Const. Art. I, § 10, cl. 1, the clause’s definition is nevertheless settled. See Collins v. Youngblood, 497 U.S. 37, 110 S.Ct. 2715, 2719, 111 L.Ed.2d 30 (1990). The prohibition against ex post facto laws, which “applies only to penal statutes which disadvantage the offender affected by them,” id. 110 S.Ct. at 2718, assures that innocent conduct is not made criminal after the fact and that greater punishment is not imposed after the fact. See Weaver v. Graham, 450 U.S. 24, 28, 101 S.Ct. 960, 963, 67 L.Ed.2d 17 (1981), The definition is fully stated as follows:
It is settled, by decisions of this Court so well known that their citation may be dispensed with, that any statute which punishes as a crime an act previously committed, which was innocent when done; which makes more burdensome the punishment for a crime, after its commission, or which deprives one charged with crime of any defense available according to law at the time that the act was committed, is prohibited as ex post facto.
Collins, 110 S.Ct. at 2719 (quoting Beazell v. Ohio, 269 U.S. 167, 169-70, 46 S.Ct. 68, 68, 70 L.Ed. 216 (1925)). The Court in Collins rejected broader definitions given earlier that an ex post facto law is one “ ‘in relation to the offence or its consequences, [that] alters the situation of a party to his disadvantage.' ” Collins, 110 S.Ct. at 2720 (emphasis added) (quoting Kring v. Missouri, 107 U.S. (17 Otto.) 221, 228, 2 S.Ct. 443, 449, 27 L.Ed. 506 (1882)).
Emerging clearly from this discussion is the conclusion that a statute that is not penal cannot be ex post facto. Thus it cannot be said that the DNA testing, itself, runs afoul of the Ex Post Facto Clause. We agree with the district court’s finding that:
The requirement that prisoners provide blood samples is not punitive in nature .... The blood sample is taken and analyzed for the sole purpose of establishing a data bank which will aid future law enforcement.
In light of our determination that the program withstands challenge under ■ the Fourth Amendment, the blood testing requirement legally can be implemented, and as is the case regarding any valid prison regulation, violators can be administratively punished for their failure to provide samples.
The Ex Post Facto Clause does not prevent prison administrators from adopting and enforcing reasonable regulations that are consistent with good prison administration, safety and efficiency. As we stated in Gaston v. Taylor, 946 F.2d 340, 343 (4th Cir.1991) (en banc),
[Cjhanges in a prisoner’s location, variations of daily routine, changes in conditions of confinement (including administrative segregation), and denials of privileges—matters which every prisoner can anticipate are contemplated by his original sentence to prison—are necessarily functions of prison management that must be left to the broad discretion of prison administrators.
It is precisely because reasonable prison regulations, and subsequent punishment for infractions thereof, are contemplated as part of the sentence of every prisoner, that they do not constitute additional punishment and are not classified as ex post fac-to. Moreover, since a prisoner’s original sentence does not embrace a right to one *310set of regulations over another, reasonable amendments, too, fall within the anticipated sentence of every inmate. We therefore conclude that neither Virginia’s blood testing requirement, itself, nor the infliction of punishment within the terms of the prisoners’ original sentence for a violation of the requirement, is ex post facto.3
The inmates present a different problem, however, in challenging the apparent authority of Virginia’s prison officials to enforce the blood testing requirement by deferring the inmate’s release date into the mandatory parole period until the blood sample is provided. While § 53.1-159 explicitly guarantees an inmate’s “release on parole[ ] ... six months prior to his date of final discharge,” unless the Parole Board determines that release would constitute a “clear and present danger” to someone in the community,4 see Va.Code Ann. § 53.1-159, the DNA data bank statute suggests that “[notwithstanding the provisions of 53.1-159,” an inmate’s release can be delayed until he provides a blood sample. Thus, prior to the enactment of § 19.2-310.2 every prisoner received an automatic six-month reduction of sentence unless he constituted a “clear and present danger” to society. Whereas, if § 19.2-310.2 were to be enforced to deny the prisoner that automatic release for refusing to provide a blood sample, the prisoner would be held beyond the time of release contemplated by the original sentence and a term of his sentence, thereby, would be made more onerous ex post facto. See Weaver, 450 U.S. at 36, 101 S.Ct. at 968.
In reliance on Warden v. Marrero, 417 U.S. 653, 661-64, 94 S.Ct. 2532, 2537-39, 41 L.Ed.2d 383 (1974), we have held that parole eligibility is a facet of the sentence imposed, and that, by deferring the eligibility date, the state imposed on the defendant after-the-fact punishment when denying a sentence benefit that he had at the time the offense was committed. Schwartz v. Muncy, 834 F.2d 396, 397-98 (4th Cir.1987). See also Fender v. Thompson, 883 F.2d 303, 307 (4th Cir.1989). We similarly conclude that if § 19.2-310.2 were to be enforced to deny an inmate convicted of a crime before July 1, 1990, the mandatory parole inherent in the original sentence given him, the prohibition against ex post facto laws would be violated.
Thus, the 1990 Virginia statute does not qualify as an ex post facto law with respect to its requirement that blood samples be provided by inmates or its possible effect in authorizing prison punishment, the denial of good-time credits, or consideration by the parole board in granting discretionary parole to compel the inmate to provide a sample, because it does not thereby alter any prisoner’s sentence for past conduct. However, the continued incarceration beyond a time six months prior to the end of the actual sentence of an inmate convicted prior to the enactment of § 19.2-310.2, for any reason not reflected in the terms of the mandatory parole provision, would constitute a retroactive extension of the inmate’s sentence which is prohibited by the Ex Post Facto Clause.
IV
In summary, we agree for the most part with the district court’s decision granting summary judgment to the directors of Virginia’s Department of Corrections and Division of Forensic Science. Considering the inmates’ questionable claim of privacy to protect their identification and the minimal *311intrusion resulting from taking a small sample of blood, the Commonwealth’s interest in combatting and deterring felony recidivism justifies the involuntary taking of the sample and the creation of the DNA data bank as reasonable in the context of the Fourth Amendment. Furthermore, it is our conclusion that Virginia’s requirement that all incarcerated felons provide a blood sample to prison medical personnel prior to the inmate’s release does not constitute a retroactive increase in the sentence of any inmate in violation of the Ex Past Facto Clause except to the extent that the first five words of the sentence of § 19.2-310.2, providing
Notwithstanding the provisions, of 53.1-159, any person convicted of a felony who is in custody after July 1, 1990, shall provide a blood sample.prior to his release (emphasis added),
authorize a modification of mandatory parole. We hold that those five words therefore are unconstitutional and may not be enforced to modify the mandatory parole period. See Va.Code Ann. § 1-17.1 (Michie 1987) (“The provisions of statutes in this Code or the application thereof to any person or circumstances which are held invalid shall not affect the validity of other statutes, provisions or applications of this Code_”). See also City of Portsmouth v. Citizens Trust Co., 216 Va. 695, 222 S.E.2d 532, 535 (1976) (severing unconstitutional mandate, even without a severability clause, because “[djeletion of the invalid [provision did] not alter the effect of the ordinance in fulfilling the purpose expressed”). Because the purpose of combat-ting and deterring, recidivism through the establishment of a DNA identification program easily can be accomplished without application of the ex post facto sanction, we conclude that “the legislature would be satisfied with what remains after the invalid part has been eliminated.” City of Waynesboro v. Keiser, 213 Va. 229, 191 S.E.2d 196, 200 (1972). Accordingly, the judgment of the district court is affirmed in part and reversed in part.
AFFIRMED IN PART AND REVERSED IN PART.
. Although § 19.2-310.2 also requires felons convicted on or after July 1, 1990, but not sentenced to a term of confinement to submit to a blood test as a condition of their sentence, that requirement is not challenged in this case.
. Because we consider the cases which involve the Fourth Amendment rights of prison inmates to comprise a separate category of cases to which the usual per se requirement of probable cause does not apply, there is no cause to address whether the so-called “special needs" exception, relied on by the district court, applies in this case. We do, however, find support for our holding in the fact that the Supreme Court has not categorically required individualized suspicion in the case of every search which advances a law enforcement objective. Only recently it concluded that a "slight” or "minimal” intrusion caused by the short stop of an automobile at a checkpoint, although directed at a class of people without individualized suspicion, may be justified as reasonable under the Fourth Amendment by a weightier interest advanced by the search. See Michigan Dep't Of State Police v. Sitz, 496 U.S. 444, 110 S.Ct. 2481, 2488, 110 L.Ed.2d 412 (1990) (approving use of sobriety checkpoint to deter drunk driving).
. While we can anticipate that blood samples will be taken in a manner and under circumstances best determined by prison administrators, if prison officials compel compliance by prison punishment, loss of good-time credits, or adverse recommendations for parole, some legal process may be required. The district court already concluded that when a prisoner violates the statute and becomes exposed to disadvan-tagement, he "must be given some process before he is held beyond his established parole release date." That ruling has not been appealed and is not before us. Suffice it to say that whatever punishment or disadvantagement is imposed results, not by reason of conduct that took place before enactment of the statute, so as to become retrospective, but from conduct that occurred after enactment in refusing to comply with a reasonable regulation.
. Not relevant to this discussion, § 53.1-159 also requires that a minimum of three months be served prior to release on mandatory parole.