concurring.
While joining the court’s opinion without reservation, I offer some additional observations.
Courts that have dealt with constitutional challenges to DNA-collection statutes frequently have lumped together all persons subject to these laws. Yet there are at least four major categories, potentially subject to differing legal analysis.
Prisoners make up the first category. Their privacy interests are extinguished by the judgments placing them in custody. As a result, “the Fourth Amendment proscription against unreasonable searches does not apply within the confines of the prison cell.” Hudson v. Palmer, 468 U.S. 517, 526, 104 S.Ct. 3194, 82 L.Ed.2d 393 (1984). See also, e.g., Johnson v. Phelan, 69 F.3d 144 (7th Cir.1995). Testing prisoners’ blood, urine, saliva, or hair for drugs is routine and does not require individual suspicion. DNA is present in all living cells, so it may be obtained from any of the blood or other samples regularly collected from prisoners. Indeed, prisons may conduct body-cavity searches without suspicion, see Bell v. Wolfish, 441 U.S. 520, 99 S.Ct. 1861, 60 L.Ed.2d 447 (1979), though nothing of the kind would be allowed for free persons. Collecting DNA is much less intrusive. Prisons, moreover, have a constitutional duty to attend to inmates’ medical needs, and the discharge of this duty requires them to learn details about the inmates’ medical conditions. That will entail the drawing of blood (how *680else could the prison learn whether an inmate is diabetic?), and like other specimens the Inmates’ blood may be put to multiple uses, including preservation of DNA, for the fourth amendment does not control how properly collected information is deployed. Use of DNA is in this respect no different from use of a fingerprint; only the method of obtaining the information differs, and for prisoners that is a distinction without importance.
Persons on conditional release — parole, probation, supervised release, and the like — are the second category. They have acquired additional liberty but remain subject to substantial controls. People who object to the conditions of release before the end of their sentences may say no and remain in prison; if they say yes, they have consented to the conditions. See United States v. Cranley, 350 F.3d 617 (7th Cir.2003). (Society may restore a felon’s freedom in increments; it does not face an all-or-none choice.) One common condition of release is submission to tests for drugs, without the need for person-specific suspicion. DNA may be extracted from samples obtained through these tests without any incremental invasion of privacy. And if such an incremental invasion is required: well, it is beyond dispute that conditions of release related to enforcing the criminal laws are valid, because refraining from new crime is one vital condition of parole and like states. Thus parolees may be required to submit to searches of their homes without probable cause, see Griffin v. Wisconsin, 483 U.S. 868, 107 S.Ct. 3164, 97 L.Ed.2d 709 (1987); United States v. Knights, 534 U.S. 112, 122 S.Ct. 587, 151 L.Ed.2d 497 (2001), to report regularly to government offices to give accounts of their activities, to get approval for new employment or living arrangements, and so on. DNA collection is less invasive than a search of one’s home, and as information from DNA may be very helpful in solving crimes (and thus enforcing a condition of release), there is no problem under the fourth amendment.
Felons whose terms have expired are the third category. Established criminality may be the basis of legal obligations that differ from those of the general population. “A broad range of choices that might infringe constitutional rights in free society fall within the expected conditions ... of those who have suffered a lawful conviction.” McKune v. Lile, 536 U.S. 24, 36, 122 S.Ct. 2017, 153 L.Ed.2d 47 (2002). One need only think of Megan’s Law and its variations across the nation. See Connecticut Department of Public Safety v. Doe, 538 U.S. 1, 123 S.Ct. 1160, 155 L.Ed.2d 98 (2003). Felons likewise are subject to limits on ownership of weapons and participation in certain occupations (including law). Greater post-release restrictions on those with a known criminal propensity make it possible to curtail the time felons must linger in prison. Collecting felons’ DNA, like collecting their fingerprints, handwriting exemplars, and other information that may help solve future crimes (and thus improve the deterrent force of the criminal sanction) is rationally related to the criminal conviction. (That collection of Felon A’s DNA may help Accused B show his innocence of a charge is a benefit into the bargain.)
Those who have never been convicted of a felony are the last distinct category. What is “reasonable” under the fourth amendment for a person on conditional release, or a felon, may be unreasonable for the general population. Just as parolees’ homes may be searched without a warrant or probable cause, while both are required to search a free person’s home, so it may be that collection of DNA samples from the general population would require person-specific cause — or at least a “special need,” whatever the meaning of that *681phrase in recent decisions turns out to be. See Indianapolis v. Edmond, 531 U.S. 32, 121 S.Ct. 447, 148 L.Ed.2d 333 (2000); Ferguson v. City of Charleston, 532 U.S. 67, 121 S.Ct. 1281, 149 L.Ed.2d 205 (2001). The majority in United States v. Kincade, 345 F.3d 1095 (9th Cir.2003), which held that the DNA Analysis Backlog Elimination Act of 2000, 42 U.S.C. § 14135a, violates the fourth amendment, made a fundamental error when it applied the “special need” approach of Edmond and Ferguson to persons on supervised release from criminal sentences that have yet to expire. That confuses the fourth category with the second. Knights, which held that conditions of supervised release may be enforced without regard to whether they would be “reasonable” as applied to the general population, was issued after Edmond and Ferguson; the Justices evidently perceive that these decisions cover different domains.
This appeal does not present the question whether DNA could be collected forcibly from the general population, and I understand the court’s reference to Edmond and Ferguson to mean no more than that these decisions are compatible with collecting and preserving DNA from persons in the first two categories, and likely from those in the third. There will be time enough to address the fourth if and when a more general statute about the collection and use of medical information should be enacted.