concurring in part and dissenting in part.
I am in full agreement with much of the majority’s opinion. Construing 28 U. S. C. § 1821, which authorizes compensation at the rate of $20 per day to “[a] witness attending in any court of the United States . . . ” the Court holds today that a person held in jail as a material witness1 is “attending in . . . court” each day that the *592pertinent judicial proceeding is underway, even if the witness is not physically present in the courtroom. But the majority also holds that a jailed witness is not “attending in” court prior to the inception of the judicial proceeding, even though he is held in custody for no other purpose than to insure his appearance to give testimony at trial. I reject that conclusion because, in my view, it works an obvious and severe hardship on an incarcerated witness, because it is compelled neither by the language nor the purposes of the statute, and because the statute so construed would be unconstitutional under the Due Process Clause of the Fifth Amendment.
I
In addition to providing compensation of $20 per day for “each day’s attendance and for the time necessarily occupied in going to and returning from” the court where the witness is to testify, the statute also authorizes, in certain cases, an “additional allowance of $16 per day for expenses of subsistence.” 28 U. S. C. § 1821. And the same statute states that “[w]hen a witness is detained in prison for want of security for his appearance, he shall be entitled, in addition to his subsistence, to a compensation of $1 per day.”
In construing these statutory provisions, petitioners (citizens of Mexico who entered the United States illegally), respondent, and the Court agree on two points: first, that a jailed material witness is entitled to compensation of $1 per day for each day that he spends in confinement; and second, that a jailed material witness is entitled to the additional compensation of $20 per day for each day that a trial is in progress and that the witness is physically present in the courtroom. The point in contention is whether or not the jailed witness should receive the additional compensation of $20 per day during the time after he is taken into custody, but *593before he is physically present in court. Petitioners contend that he should. Respondent contends that he should not. The Court holds that he should receive the compensation for each day that the trial is in progress (whether or not he actually appears in court), but that he should not receive it for the days spent in custody before the trial is under way.
The Court predicates its conclusion on a superficially plausible reading of the literal terms of the statute:
“The petitioners’ interpretation of ‘attendance’ as beginning with the first day of incarceration slights the statutory requirement that attendance be in court. A witness might be detained many days before the case in which he is to testify is called for trial. During that time there is literally no court in session in which he could conceivably be considered to be in attendance.” Ante, at 583.
The Court holds, in other words, that if the court is not in session, then a jailed material witness cannot be said to be “attending in . . . court.” (Emphasis added.) But the correct interpretation of the phrase, “in court,” is not as obvious as it would at first appear. Read literally, the phrase would appear to require that the witness spend the day within the four walls of the courtroom, or, at the very least, the courthouse. Yet the Court recognizes, and the Government concedes, that a witness can be “in court” even if he is in a hotel room or a restaurant. I share the view that physical presence in the courtroom is not required to bring a witness within the reach of the statute. But I cannot accept the Court’s conclusion that a witness is “in court” or not “in court,” depending on whether or not the judicial proceeding is technically under way.
Unfortunately, the Government has not described its practice in compensating witnesses under § 1821 with *594the kind of specificity that would simplify our analysis. It would seem plausible, however, to assume that the practice might be as follows: A witness subpoenaed to appear on Tuesday morning may spend all of Monday en route to the courthouse, only to learn on Tuesday that the case will not be called as early as expected. If the witness waits in the witness room all day each day until the case is finally called on Friday, it would seem reasonable to assume that he is entitled to compensation for his attendance on Tuesday, Wednesday, and Thursday, even though the proceeding did not begin until Friday. Whatever the Government’s practice in such a case, I would hold that the payment of compensation for those three days would be permitted, if not required, by the terms of the statute. Yet under the Court’s rigid analysis of the phrase, “in court,” it would be unlawful for the Government to compensate the witness, except for the days spent traveling to and from the courthouse, for any day except Friday. The Court is apparently bound to hold that notwithstanding the physical presence of the witness in the courthouse, he was not “in court” because the court was not yet in session.
The obvious shortcoming of the Court’s analysis is its disregard, in construing the critical statutory phrase, of the purposes of the statute. The statute is grounded on the view that a subpoena to appear and give testimony will often entail substantial disruption of one’s affairs, a loss of income, and considerable inconvenience. These dislocations, for which Congress has authorized compensation,2 will exist whether a witness is required to wait in a witness room, a prosecutor’s office, a courtroom, or *595a hotel room. For that reason, the Court is correct in its conclusion that a witness may be “in court” for the purposes of the statute even though he is not, in fact, in the courthouse. But that same purposive analysis refutes the Court’s suggestion that the pendency of a judicial proceeding is a precondition to the payment of witness fees. Surely the fact that the court is not yet in session is small comfort to the witness who is required to appear and wait for the calling of his case. His daily loss of income does not mysteriously increase as soon as the judge appears behind the bench. Nor, if he is unlucky enough to be held in custody for want of bail, does the infringement on his liberty become less burdensome or the assault on his dignity less severe. Whatever the status of the judicial proceeding, it remains clear that the witness is held in jail for a single purpose: to serve the interests of the court. And it is the unquestioned purpose of the statute to insure that witnesses who are inconvenienced to serve the interests of the court are compensated, at least in part, for the service they have given. I cannot ascribe to Congress the essentially irrational view that a day spent in attendance on a pending trial is inherently a day more worthy of compensation than a day spent in attendance on a trial that is not yet under way. Nothing should or was intended to turn on whether a trial is actually in progress.
II
My conclusion that the majority has misconstrued the statute is fortified by the conviction that the statute, as interpreted by the Court, would be invalid under the Due Process Clause of the Fifth Amendment. Bolling *596v. Sharpe, 347 U. S. 497 (1954). The majority discerns a
“reasonable basis for distinguishing the compensation paid for pretrial detention from the fees paid for attendance at trial. Pretrial confinement will frequently be longer than the period of attendance on the court, and throughout that period of confinement the Government must bear the cost of food, lodging, and security for detained witnesses. Congress could thus reasonably determine that while some compensation should be provided during the pretrial detention period, a minimal amount was justified, particularly in view of the fact that the witness has a public obligation to testify.” Ante, at 590.
In my view, that assertion is inadequate to the task of justifying this discriminatory classification scheme. First, as construed by the Court, the scheme clearly does not treat jailed material witnesses in a manner which is in any sense equivalent to the treatment of subpoenaed witnesses. Rather, the Court establishes two distinct classes of inconvenienced witnesses: those who are burdened by a subpoena to appear, and who receive compensation for each day of dislocation; and those who are burdened by a term in jail, but who are compensated only for the days of dislocation which follow the inception of trial. The Court apparently denies this inequality, asserting that “[d]uring the period that elapses before his attendance on a court, a witness who is not incarcerated gets no compensation whatever from the Government. An incarcerated witness, on the other hand, gets one dollar a day during that period, in addition to subsistence in kind.” Ante, at 590. But the appropriate point of comparison is not the treatment of incarcerated witnesses before trial with the treatment of nonincarcerated wit*597nesses before trial. The statement that a subpoenaed witness receives no compensation for the period which precedes the onset of trial is true but irrelevant. Naturally the witness receives no compensation; he has sustained no injury. By hypothesis, the subpoena directs the witness to appear at a time when trial is at least scheduled to begin. In practical effect, therefore, the subpoenaed witness is compensated in full for each day of inconvenience, while the jailed witness may endure the “inconvenience” of a lengthy term in jail and receive significant compensation only for the days of confinement which happen to coincide with trial.
Moreover, this discrimination- against jailed witnesses cannot be justified by reference to the fact — again, true but irrelevant — that the “witness has a public obligation to testify.” Ante, at 590. The identical “public obligation” is imposed on the subpoenaed witness, and the existence of the obligation does not rationalize the heavier burden placed on the jailed witness in seeking compensation for his days of dislocation. And since the jailed witness carries the same obligation to testify both before and after trial has begun, its existence does not explain a scheme that provides significant compensation only for days of confinement during trial.
If the statutory scheme is to be upheld, it can only be on the theory that Congress has made a rational attempt to impose some limits on the amount of money which will be paid out to any given witness under the scheme. I can assume that the imposition of such a ceiling on expenditures is, in itself, a permissible goal. And since witness fees could, in some instances, reach staggering amounts, I can assume that Congress has the power to impose an across-the-board cutoff — e. g., $1,000 per witness — on the fees allowable under the Act. But these assumptions do not reheve us of the obligation to determine whether the particular approach Congress *598has used in imposing a cutoff is sufficiently rational to withstand constitutional 'attack. Cf. Dandridge v. Williams, 397 U. S. 471, 483-487 (1970). I conclude that it is not.
As the Court construes the. statutory scheme, a material witness who is held in jail for four months in anticipation of a one-day trial will receive in compensation $141— $1 per day for each of 120 days, and $21 for the day of trial. By contrast, a witness who is subpoenaed to appear on the first day of trial but who, as a result of preliminary motions, adjournment, and miscellaneous delays, is not called to appear until two weeks have passed, will receive $280 in compensation, plus a subsistence allowance. However legitimate the governmental, interest in imposing some limit on the expenditure of money to witnesses, the mere assertion of that interest cannot save a classification scheme that pays to a witness who spends two weeks in a hotel a sum of money greatly in excess of the amount made available to one who spends four months in the less congenial atmosphere of a courthouse jail. I can see no rational basis for this appalling difference in treatment.3
*599The classification scheme we uphold today cannot be considered a rational attempt to preserve the Government’s financial resources.4 Regrettably, it seems to *600me little more than an attempt to punish those who are unable to give bail as a guarantee of their appearance at trial, and who, almost by definition, lack the power and resources to remedy their unfortunate plight. As my Brother Douglas points out, “[w]e cannot allow the Government's insistent reference to these Mexican citizens as ‘deportable aliens’ to obscure the fact that they come before us as innocent persons who have not been charged with a crime or incarcerated in anticipation of a criminal prosecution.” Post, at 604. They have been held in custody only to insure their presence at trial. I would not impute to Congress an intent to penalize these petitioners by holding the injury they have suffered less worthy of compensation than the inconvenience to a witness who is subpoenaed to appear at trial. I would hold, consistently with a fair reading of the statute in light of its purposes, that petitioners are entitled to compensation at the rate of $21 per day for each day they spend in custody while awaiting the call to appear in court.
Fed. Rule Crim. Proc. 46 (b), at the time this case arose, provided that where a witness’ testimony was “material” in any criminal proceeding and where it might become impracticable to secure the presence of the witness by subpoena, the court might require the witness to give bail for his appearance. If the witness failed to give bail, the court might order his incarceration pending final disposition of the proceeding in which his testimony was needed.
The Government argues at length that Congress did not intend to provide full compensation to a witness or to insure the witness against all lost earnings. See Brief for United States 16-24. The Government does not dispute, however, that the congressional pur*595pose was to provide at least partial compensation for the expenses, dislocation, and income loss attributable to compelled attendance as a witness.
Of course, where the Government detains a material witness pending trial, its total financial burden is not limited to the payment of $1 per day under 28 U. S. C. § 1821. The Government also assumes the expense of feeding and housing the incarcerated witness. Nevertheless, I cannot conclude that this added expense affords a rational basis for imposing an arbitrary ceiling on the payment of witness fees to a jailed witness. First, the Government makes no attempt to justify the statute on this ground, and we are not advised of the marginal cost to the Federal Government of holding a material witness in an existing penal facility. Second, the legislative history of the scheme evidences no particular congressional concern for the costs of incarceration, nor any effort to limit the payment of witness fees because of this added expense. Third, even if the marginal costs of incarceration are substantial, that fact cannot explain the absence of any limits whatsoever on the witness fees that can be paid to a nonincarcerated witness. And since a nonincarcerated wit*599ness may be eligible for a subsistence allowance of $16 per day in addition to the $20 daily fee, the amount of money involved can be very large indeed. Finally, and most important, while the Government has an obvious interest in limiting its total expenditure on witnesses — including the payment of fees, subsistence allowances, and incarceration costs — that interest cannot explain the payment of higher per diem fees to nonincarcerated witnesses than to incarcerated witnesses. Even if the cost of keeping a witness in jail is $36 per day, which is the amount paid each day to a nonincarcer-ated witness, it does not follow that the payments are equivalent from the standpoint of the witnesses. The jailed witness is inconvenienced no less than the subpoenaed witness, yet his rate of compensation is dramatically, and inexplicably, less.
Nor can the scheme be justified on the theory that one who is too poor to give bail deserves only minimal compensation because he is unlikely to incur any great financial loss during the period of incarceration. The fact that a witness is unable to give bail is hardly an indication that he is unemployed. In any case, the statute is designed to compensate the witness not only for the loss of income, but also for the inconvenience and disruption of his personal affairs. Inconvenience is not the exclusive property of the rich. Moreover, the witness who cannot give bail is likely to be the one most in need of compensation to pay the expenses his family will inevitably incur while he waits in jail for the beginning of trial. As enacted by Congress, the scheme was thought to provide compensation in an amount that is “more or less arbitrary, but considered to be reasonably fair to the average witness.” S. Rep. No. 187, 81st Cong., 1st Sess., 2. There is no indication that Congress thought some witnesses were so poor that they could be deemed indifferent to compensation.
Thus, the Government’s assertion that “payment of $21 per day would serve as a chance bonus” for persons like petitioners who presumably earn less than that amount per day, Brief for United States 31, misses the point of the statutory scheme. By that reasoning, the scheme would offer the same “chance bonus” to a witness who earns $50,000 per year, but who is not required to perform a daily service to earn that income. Wealth is not a guarantee that income loss is substantial, just as poverty is not a guarantee that the income loss is trivial.