In this appeal, defendant-appellant Daryl E. Singleterry contests his jury conviction and resulting sentence for violation of federal drug trafficking laws. Singleterry raises two issues for our consideration. First, he protests the district court's refusal to instruct the jury to determine whether the prosecution produced sufficient evidence to establish the trustworthiness of his voluntary, extrajudicial confession. Second, Singleterry, who is black, maintains that his sentence violates the equal protection component of the Fifth Amendment because the difference in punishment for cocaine base ("crack") offenses and cocaine ("cocaine powder") offenses is either irrational or racially discriminatory. Finding neither argument persuasive, we affirm.

On January 14, 1993, Maine law enforcement agents, responding to reports of drug dealing at the Days Inn in Kittery, Maine, commenced surveillance of the motel. That evening, they observed Jamee Landry, an associate of Singleterry, exit Room 225 with George Wilson, another Singleterry associate and suspected drug dealer. The two entered Landry's car and drove to Portsmouth, New Hampshire, where the agents lost their trail. Early the next morning, after they saw Landry enter Room 225, the agents executed warrants to search both Room 225 and Landry's car.

The search revealed a number of items probative of ongoing, armed drug trafficking. The agents first entered and searched Room 225, where they found Singleterry and Landry. They seized $2061 and a wallet containing Singleterry's driver's license from the pocket of a jacket on a night table in the room. Elsewhere in the room, the agents discovered two savings account passbooks, both in Singleterry's name, with a combined balance of $5100. In Landry's car, the agents found a plastic bag containing 6.46 grams of crack cocaine in the glove compartment, a leather gun holster on the front passenger seat, as well as a fully loaded semi-automatic handgun under the same seat.

After this search concluded, the agents arrested Singleterry, and properly informed him of his "Miranda rights." Singleterry then provided the agents with a voluntary confession telling them that he personally paid $250 to his source in Lawrence, Massachusetts, for the cocaine base found in the vehicle. He also admitted that he had stolen the handgun seized by the agents, explaining that he needed the handgun to protect himself from individuals who were jealous of his cocaine business. In addition, Singleterry told the agents that he did not have a job, that he had been dealing cocaine base for a considerable period of time, and that the cash seized from his jacket pocket as well as the money in his savings accounts were proceeds from his sale of cocaine base in the Portsmouth, New Hampshire, area. Finally, Singleterry stated that, as in this instance, he purchased most of the cocaine base he sold from a source in Lawrence or Lowell, Massachusetts. According to Singleterry, he would ordinarily pay $250 for a quarter ounce of cocaine base and then sell it for $1250.

Singleterry was charged in a three count indictment with possession with intent to distribute cocaine, 21 U.S.C. Secs. 841(a)(1) and 841(b)(1)(B)(iii) (1988 & Supp. IV 1992) (Count I), the use and carrying of a firearm in connection with a drug trafficking offense, 18 U.S.C. Sec. 924(c) (1988 & Supp. IV 1992) (Count II), and deriving certain personal property from proceeds obtained as the result of drug trafficking activity, 21 U.S.C. Sec. 853 (1988) (Count III). The parties agreed to have the district court decide Count III on the basis of the trial evidence.

At trial, the government introduced evidence probative of the facts described above, relying heavily on the agents' live testimony concerning Singleterry's confession. At the close of the government's case in chief, the defense moved for judgment of acquittal. See Fed.R.Crim.P. 29(a). Defendant's primary contention was that the government's evidence could not suffice to support a conviction because the government did not adequately corroborate Singleterry's confession. See Opper v. United States, 348 U.S. 84, 75 S. Ct. 158, 99 L. Ed. 101 (1954) (prohibiting convictions on the basis of uncorroborated confessions). The government argued, inter alia, that there was ample evidence to demonstrate the truth and accuracy of the confession. The district court reserved judgment until the close of all the evidence. After the defense presented no evidence, the court denied defendant's motion in a detailed ruling from the bench.

Singleterry timely requested a jury instruction that "as a matter of law a confession alone is not sufficient evidence upon which to convict the defendant, that the confession must be accompanied by additional corroborative [evidence] or sufficient indicia of reliability." The district court refused to do so, explaining that the corroboration inquiry is for the court and not the jury. According to the district court, the role of the jury is simply to consider whether the evidence establishes each element of the offense beyond a reasonable doubt, although the jury is free to question the probative value of a confession in light of the strength or weakness of the corroborative evidence.

After deliberating for less than an hour, the jury convicted Singleterry on Counts I and II. The district court later issued an order of forfeiture in resolution of Count III.

At sentencing, the district court found that the offense level, including relevant conduct, involved a total of 73.66 grams of cocaine base, resulting in a base offense level of 32. United States Sentencing Commission, Guidelines Manual, Sec. 2D1.1 (Nov.1993); see also 21 U.S.C. Sec. 841(b)(1)(B) (prescribing minimum and maximum sentences). Because Singleterry had knowingly given false testimony at a pre-trial suppression hearing, the court added a two-level enhancement for obstruction of justice. U.S.S.G. Sec. 3C1.1. With a total adjusted base offense level of 34 and a criminal history category of III, the guideline range on Count I was 188 to 235 months.1 U.S.S.G. Ch. 5, Pt. A. The district court selected the minimum sentence of 188 months, imposing as well the consecutive 60 month sentence mandated by 18 U.S.C. Sec. 924(c) for the firearm offense. In another ruling from the bench, the district court rejected Singleterry's argument that stiffer penalties for cocaine base offenses, as opposed to cocaine powder offenses, violate Singleterry's right to equal protection of the law.

A. Trustworthiness of Confessions and the Role of the Jury

Singleterry contends that the district court committed legal error when it refused to instruct the jury on the need for corroboration of his confession. Specifically, Singleterry urges us to adopt one of two propositions. First, he suggests that, when the government's case rests primarily on a defendant's confession, the district court must instruct the jury to find the confession to be trustworthy before considering it as evidence of guilt. Second, Singleterry asserts that, even in the absence of a general rule mandating such an instruction, the district court is obliged to instruct the jury on the corroboration requirement where the evidence of trustworthiness is so weak that a jury might differ from the court in its resolution of the question.

Whether the court must assign such a role to the jury is a pure question of law subject to plenary review. See, e.g., United States v. Gallo, 20 F.3d 7, 11 (1st Cir.1994) (holding that de novo review is customary for questions of law) (citing In re Howard, 996 F.2d 1320, 1327 (1st Cir.1993)). Thus, although the district court's reasoning may prove persuasive, and its conclusion coincide with our own, we are free to reject a reasonable reading of the law in favor of the interpretation we view as correct.

To begin with, we note that a defendant's own statements are never considered to be hearsay when offered by the government; they are treated as admissions, competent as evidence of guilt without any special guarantee of their trustworthiness. See Fed.R.Evid. 801(d)(2) & advisory committee's note; see also United States v. Barletta, 652 F.2d 218, 219 (1st Cir.1981). Nevertheless, there is a danger that the jury will rush to credit a confession without seriously considering whether the defendant confessed to a crime he did not commit. As a result, the federal courts have adopted common law rules designed to prevent a jury from convicting the defendant solely on the basis of an untrustworthy confession. The general rule is that a jury cannot rely on an extrajudicial, post-offense confession, even when voluntary, in the absence of "substantial independent evidence which would tend to establish the trustworthiness of [the] statement." Opper v. United States, 348 U.S. 84, 93, 75 S. Ct. 158, 164, 99 L. Ed. 101 (1954). See also Smith v. United States, 348 U.S. 147, 75 S. Ct. 194, 99 L. Ed. 192 (1954); Warszower v. United States, 312 U.S. 342, 61 S. Ct. 603, 85 L. Ed. 876 (1941); United States v. O'Connell, 703 F.2d 645 (1st Cir.1983).2 The Court has explained that independent proof of the commission of the charged offense is not the only means of establishing the trustworthiness of the defendant's confession; another "available mode of corroboration is for the independent evidence to bolster the confession itself and thereby prove the offense 'through' the statements of the accused." Smith, 348 U.S. at 156, 75 S.Ct. at 199.3

The doctrinal nature and procedural concomitants of the trustworthiness requirement announced in Opper are not entirely clear. Traditionally, the district court makes a preliminary determination as to whether testimony about the confession is sufficiently trustworthy for the jury to consider the confession as evidence of guilt. See McCormick Sec. 145, at 562; Corey J. Ayling, Comment, Corroborating Confessions: An Empirical Analysis of Legal Safeguards Against False Confessions, 1984 Wis.L.Rev. 1121, 1140 (hereinafter "Ayling"). In this respect, the Opper rule essentially functions as a federal common law rule regulating the admission of statements which "are much like hearsay, [having had] neither the compulsion of the oath nor the test of cross-examination." Opper, 348 U.S. at 90, 75 S.Ct. at 163. See also Ayling, supra, at 1136-37 & n. 66 (arguing that the corroboration rule "governs the admissibility of evidence").4

At the same time, courts often characterize corroboration requirements as governing the sufficiency of the evidence. See, e.g., Warszower, 312 U.S. at 347-48, 61 S.Ct. at 607 (holding that "[a]n uncorroborated confession ... does not as a matter of law establish beyond a reasonable doubt the commission of a crime"); O'Connell, 703 F.2d at 647-48 (analyzing corroboration issue in rejecting challenge to sufficiency of evidence); McCormick, supra, Sec. 145, at 561-63. In contrast to a simple rule of admissibility, a rule of sufficiency might theoretically allow the trial judge to instruct the jury to make the final determination as to whether a confession has been corroborated. See id. (reporting that some state courts treat the corroboration requirement as a jury issue); Ayling, supra, at 1136-41. The Supreme Court has not ruled on the question, and neither this circuit nor any other circuit has adopted such a broad approach. But cf. United States v. Marshall, 863 F.2d 1285, 1287 (6th Cir.1988) (holding that the district court should have instructed the jury on the corroboration requirement where "[t]he need for corroboration [was] apparent").

It is within the uncertain framework of sufficiency that Singleterry positions his appeal. Singleterry does not claim that the district court erred in admitting evidence of his confession. Nor does he assert that the district court improperly found that the confession was adequately corroborated in denying the motion for judgment of acquittal.5 Rather, Singleterry insists that, even after a court has properly admitted evidence of a confession and correctly tested the sufficiency of the evidence to support a conviction, the court has a responsibility, either generally or in certain cases, to instruct the jury to determine that the confession is trustworthy before considering it as evidence of guilt. This has never been the law in the federal courts, and we decline to adopt such a rule today.

Although we cannot accept Singleterry's theory as such, we do not mean to suggest that the district court has no continuing duty to police the jury's consideration of a confession's probative value. First, if the district court loses confidence in its earlier determination of the corroboration issue and the evidence is otherwise inadequate to support a conviction, the proper course would be to enter a judgment of acquittal. Alternatively, if the government's remaining evidence could support a finding of guilt but the jury's incurable exposure to the confession raises serious questions about the prospect of a fair trial, the proper course would be to declare a mistrial. See Stewart v. United States, 366 U.S. 1, 10, 81 S. Ct. 941, 946, 6 L. Ed. 2d 84 (1961); United States v. Sepulveda, 15 F.3d 1161, 1184 (1st Cir.1993), cert. denied, --- U.S. ----, 114 S. Ct. 2714, 129 L. Ed. 2d 840, 62 U.S.L.W. 3842 (U.S. June 20, 1994).

Second, a confession otherwise admissible under Opper may nevertheless be inadmissible "if its probative value is substantially outweighed by the danger of unfair prejudice." Fed.R.Evid. 403.6

Third, particularly where a full confession dominates the government's proof, it is fair to assume that a jury will interpret its duty to find guilt beyond a reasonable doubt to mean that it cannot simply accept a confession at face value. See D'Aquino v. United States, 192 F.2d 338, 357 (9th Cir.1951) (holding that where there is adequate corroboration of the confession "the usual instructions on presumption of innocence and reasonable doubt adequately cover[ ] all that the jury need be told upon this question of [corroboration]") (citing Pearlman v. United States, 10 F.2d 460 (9th Cir.1926)), cert. denied, 343 U.S. 935, 72 S. Ct. 772, 96 L. Ed. 1343 (1952); McCormick, supra, Sec. 145, at 564 ("Nor is there sufficient need to submit the matter to the jury, as long as the jury is adequately sensitized to the need to find all elements of the crimes charged beyond a reasonable doubt.").

Fourth, we note that a judge has wide latitude to select appropriate, legally correct instructions to ensure that the jury weighs the evidence without thoughtlessly crediting an out-of-court confession. Cf. Miller, 987 F.2d at 1465 (holding that district court properly instructed jury that it could rest guilty verdict on uncorroborated yet credible testimony of an accomplice but should "keep in mind that such testimony is always to be received with caution and weighed with great care"); United States v. Twomey, 884 F.2d 46, 53 (1st Cir.1989) (suggesting that court may "assist the jury by demonstrating to them how to go about analyzing the evidence"), cert. denied, 496 U.S. 908, 110 S. Ct. 2592, 110 L. Ed. 2d 273 (1990); Ayling, supra, at 1141 (arguing that "guidance on the means of determining the ultimate credibility of the evidence accords with the jury's role as finder of evidentiary sufficiency"). Accordingly, even if the district court has properly admitted evidence of a confession, the court has the discretion to determine that the question of trustworthiness is such a close one that it would be appropriate to instruct the jury to conduct its own corroboration analysis.

In this case, there is no indication that the district court overlooked its obligation to avoid or limit undue prejudice stemming from evidence of Singleterry's confession. The district court had no occasion to exclude the confession under Rule 403, correctly found that the confession was trustworthy, and properly instructed the jury on the government's burden of proof. Finally, in a manifestly appropriate exercise of discretion, the court directed the jury to "consider any ... facts or circumstances disclosed by the evidence ... tending to corroborate or to contradict the version of events which the witnesses have told you."

In sum, there was no error in the lower court's refusal to instruct the jury to apply the Opper trustworthiness requirement before considering Singleterry's confession to be probative of his guilt.

B. Constitutionality of Sentencing Distinction Between Cocaine Base and Cocaine Powder

Singleterry maintains that his sentence on Count I is the product of an unconstitutional distinction between offenses involving cocaine base and those involving cocaine powder. See 18 U.S.C. Sec. 841(b); U.S.S.G. Sec. 2D1.1(c) (equating 1 gram of cocaine base with 100 grams of cocaine). Singleterry did not contend below that the laws at issue are facially unconstitutional. Instead, he offered evidence in an attempt to demonstrate that the sentencing distinction between cocaine base and cocaine is either irrational, racially motivated, or both. On appeal, Singleterry essentially argues that the district court erroneously applied the relevant constitutional principles to the facts found at the sentencing hearing. We first recite the procedural rules that govern this portion of our analysis, then turn to a brief discussion of the merits.

While pure questions of law are subject to de novo review, we generally examine a district court's fact-based determinations for clear error. Williams v. Poulos, 11 F.3d 271, 278 (1st Cir.1993); In re Howard, 996 F.2d at 1327-28. Thus, the district court's findings of fact are conclusive on appeal "unless, after carefully reading the record and according due deference to the trial court's superior ability to judge credibility, we form 'a strong, unyielding belief that a mistake has been made.' " Williams, 11 F.3d at 278 (quoting Dedham Water Co. v. Cumberland Farms Dairy, Inc., 972 F.2d 453, 457 (1st Cir.1992)). The same standard of review often applies to mixed questions of law and fact, although we are less likely to defer to the district court's conclusions where proper application of the law primarily requires a clarification of the relevant legal principles. Id. at 278 & n. 11 (citing In re Howard, 996 F.2d at 1328).

The clear error standard does not apply, however, when the fact-finding at issue concerns "legislative," as opposed to "historical" facts. See generally Dunagin v. City of Oxford, 718 F.2d 738, 748 n. 8 (5th Cir.1983) (en banc) (plurality), cert. denied, 467 U.S. 1259, 104 S. Ct. 3553, 82 L. Ed. 2d 855 (1984); Menora v. Illinois High Sch. Ass'n, 683 F.2d 1030, 1036 (7th Cir.1982), cert. denied, 459 U.S. 1156, 103 S. Ct. 801, 74 L. Ed. 2d 1003 (1983); see also Lockhart v. McCree, 476 U.S. 162, 168-69 n. 3, 106 S. Ct. 1758, 1762-63 n. 3, 90 L. Ed. 2d 137 (1986) (reserving question while suggesting approval of plurality opinion in Dunagin ). "Legislative facts are those general considerations that move a lawmaking or rulemaking body to adopt a rule, as distinct from the facts which determine whether the rule was correctly applied." Menora, 683 F.2d at 1036. Accordingly, we need not defer to the lower court's assessment of the "evidence" Singleterry offers to demonstrate the irrational and racially discriminatory nature of the adoption of the distinction between cocaine base and cocaine powder offenses.

It is well settled that an irrational classification imposed by federal law is violative of the equal protection component of the Fifth Amendment's Due Process Clause. See Miranda v. Secretary of Treasury, 766 F.2d 1, 6 (1st Cir.1985) (citing Mathews v. De Castro, 429 U.S. 181, 182 n. 1, 97 S. Ct. 431, 432-33 n. 1, 50 L. Ed. 2d 389 (1976)). Singleterry contends that a distinction between cocaine base and cocaine powder is such a classification because the use of cocaine base allegedly presents no greater health threat than the use of cocaine powder. Yet Singleterry presents little or no evidence to support this contention, nor has he explained why such evidence would be dispositive of the rationality of the distinction at issue.

Even if there is no telling difference in the health effects associated with the use of different types of cocaine, it would be rational to treat cocaine base offenses more harshly for other reasons. For example, Congress could rationally seek to strengthen the deterrent effect of the narcotics laws by increasing the "cost" to a criminal of using or selling a cocaine substance that, like cocaine base, is sold at a cheaper unit price than other cocaine substances. Indeed, of the four citations to the Congressional Record that Singleterry offers in his opening brief as probative of congressional intent, each suggests that Congress has been concerned that the low price of cocaine base (in the absolute sense as well as relative to cocaine) would lead to an explosion in drug use.

In any event, the district court correctly concluded that "Congress had before it sufficient ... information to make distinctions that would justify ... more severe sentences for trafficking in or using cocaine base or crack than cocaine itself." Accord United States v. Frazier, 981 F.2d 92, 95 (3d Cir.1992) (noting that the Third Circuit, "along with every other federal court of appeals to rule on the issue, has held that the distinction between cocaine base and cocaine in the federal sentencing scheme is constitutional under rational basis equal protection review"), cert. denied, --- U.S. ----, ----, 113 S. Ct. 1661, 1662, 123 L. Ed. 2d 279 (1993).

Singleterry next argues that the harsher penalties for cocaine base offenses are unconstitutional because they have such a disproportionate effect on blacks as to give rise to an inference that Congress and the Sentencing Commission established those penalties for the purpose of racial discrimination. See Yick Wo v. Hopkins, 118 U.S. 356, 6 S. Ct. 1064, 30 L. Ed. 220 (1886). As proof of disparate impact, Singleterry offers some evidence that (1) most cocaine base users are black while most users of cocaine are white, and (2) the vast majority of sentences for cocaine base offenses are imposed on black defendants while white defendants comprise the largest share of those sentenced for cocaine offenses. In addition, Singleterry has offered some evidence that Congress anticipated such an impact because, in adopting heightened penalties for cocaine base offenses, it was attempting to address a problem afflicting lower-income urban communities.

We agree that where evidence of disparate impact leads most naturally to an inference of discriminatory purpose, the governmental classification may be subject to strict scrutiny under equal protection principles. See McCleskey v. Kemp, 481 U.S. 279, 293, 107 S. Ct. 1756, 1767, 95 L. Ed. 2d 262 (1987) (holding that " 'stark' " statistical pattern may serve "as the sole proof of discriminatory intent under the Constitution") (quoting Village of Arlington Heights v. Metropolitan Hous. Dev. Corp., 429 U.S. 252, 266, 97 S. Ct. 555, 563-64, 50 L. Ed. 2d 450 (1977)); Washington v. Davis, 426 U.S. 229, 242, 96 S. Ct. 2040, 2048-49, 48 L. Ed. 2d 597 (1976) ("[D]iscriminatory impact ... may for all practical purposes demonstrate unconstitutionality because in various circumstances the discrimination is very difficult to explain on nonracial grounds."); Gomillion v. Lightfoot, 364 U.S. 339, 341, 81 S. Ct. 125, 127, 5 L. Ed. 2d 110 (1960); Yick Wo, 118 U.S. at 373-74, 6 S.Ct. at 1072-73. But here, as we suggested in discussing the rationality of the sentencing scheme, there are racially neutral grounds for the classification that more "plausibly explain[ ]" its impact on blacks. Personnel Adm'r v. Feeney, 442 U.S. 256, 275, 99 S. Ct. 2282, 2294, 60 L. Ed. 2d 870 (1979). As a result, there is insufficient evidence "that the distinction drawn between cocaine base and cocaine was motivated by any racial animus or discriminatory intent on the part of either Congress or the Sentencing Commission." Frazier, 981 F.2d at 95 (citing United States v. Simmons, 964 F.2d 763 (8th Cir.), cert. denied, --- U.S. ----, 113 S. Ct. 632, 121 L. Ed. 2d 563 (1992), and United States v. Galloway, 951 F.2d 64 (5th Cir.1992)). But see United States v. Clary, 846 F. Supp. 768 (E.D.Mo.1994) (holding that sentencing distinction between cocaine base and cocaine powder violates equal protection principles after finding circumstantial evidence of unconscious discriminatory purpose). In short, there was no error in the district court's determination to this effect.

Finally, we note that while "[t]he equal protection obligation imposed by the Due Process Clause of the Fifth Amendment is not an obligation to provide the best governance possible," Schweiker v. Wilson, 450 U.S. 221, 230, 101 S. Ct. 1074, 1080, 67 L. Ed. 2d 186 (1981), the absence of a constitutional command is not an invitation to government complacency. Although Singleterry has not established a constitutional violation, he has raised important questions about the efficacy and fairness of our current sentencing policies for offenses involving cocaine substances. We leave the resolution of these matters to the considered judgment of those with the proper authority and institutional capacity.

For the foregoing reasons, we affirm Singleterry's conviction as well as his sentence.

So ordered.