Appellant, Darius Smith, was convicted after a jury trial of second degree murder while armed and related weapons offenses.1 Over Smith’s objection, the trial court instructed the jury on the meaning of reasonable doubt using portions of FEDERAL Judicial CenteR, PatteRN Criminal JURY Instructions, No. 21 (1988) (FJC instruction) instead of the standard instruction generally used in Superior Court, i.e., Criminal Jury Instructions for the District of Columbia No. 2.09 (4th ed. 1993) (“Redbook” instruction), for which Smith expressed a preference. See Smith v. United States, 687 A.2d 1356, 1359-60 & n. 1 (D.C.1996). In affirming the judgment of conviction, a division of this court held that “the [trial] court’s instruction, taken as a whole, correctly conveyed the government’s burden of proof under the reasonable doubt standard and did not shift or lessen that burden of proof.” Id. at 1358. We granted rehearing en banc to decide whether to adopt or approve a new instruction on reasonable doubt to replace Redbook instruction 2.09.2 After consideration of the comprehensive briefs from the parties and amicus curiae, we conclude that the standard Redbook instruction should be modified in the manner set forth in this opinion. Our reconsideration does not alter the division’s conclusion that the instruction which the trial court gave in this case did not deprive Smith of due process of law. Therefore, we affirm the judgment of conviction.
I.
The standard of proof beyond a reasonable doubt “is an ancient and honored aspect of our criminal justice system,” although one which “defies easy explication.” Victor v. Nebraska, 511 U.S. 1, 5, 114 S.Ct. 1239, 1242, 127 L.Ed.2d 583 (1994). In a criminal trial, application of that standard of proof is a requirement of due process. See id.; Cage v. Louisiana, 498 U.S. 39, 39-40, 111 S.Ct. 328, 329, 112 L.Ed.2d 339 (1990) (citing In re Winship, 397 U.S. 358, 364, 90 S.Ct. 1068, 1072, 25 L.Ed.2d 368 (1970)(other citations omitted)). The Supreme Court has held that the Constitution neither requires nor prohibits trial courts from defining proof beyond a reasonable doubt. See Victor, 511 U.S. at 5,114 S.Ct. at 1242. However, when a definition of the standard of proof is given to the jury, the instructions, taken as a whole, must convey the concept properly. See Holland v. United States, 348 U.S. 121, 140, 75 S.Ct. 127, 137, 99 L.Ed. 150 (1954).
This court en banc has never considered the issue, but a division has held that the trial court must instruct the jury on reasonable doubt. See Butler v. United States, 646 A.2d 331, 337 (D.C.1994), cert. denied, 514 U.S. 1009, 115 S.Ct. 1326, 131 L.Ed.2d 206 (1995). Although some courts have held that no attempt should be made to define the concept of reasonable doubt to the jury, we reaffirm the requirement that reasonable doubt be explained to the juries in Superior Court.3 The elimination of the requirement of an explanatory instruction would be a marked departure from the long-standing practice in this jurisdiction. Moreover, it would relegate the most fundamental, and perhaps decisive, principle in a criminal trial to random interpretation by counsel and jurors. Reasonable doubt is “perhaps the most important aspect of the closing instruction to *80the jury in a criminal trial.” Dunn v. Perrin, 570 F.2d 21, 25 (1st Cir.), cert. denied, 437 U.S. 910, 98 S.Ct. 3102, 57 L.Ed.2d 1141 (1978); see also Jackson v. Virginia, 443 U.S. 307, 315, 99 S.Ct. 2781, 2787, 61 L.Ed.2d 560 (1979) (reasonable doubt has “traditionally been regarded as the decisive difference between culpability and civil liability’). Lay jurors should not be left to undertake the important task of deciding whether the government has proven “the guilt of the accused beyond a reasonable doubt without some intelligent statement of its meaning[.]” Egan v. United States, 52 App. D.C. 384, 393, 287 F. 958, 967 (1923).
In the strongest terms, a division of the court previously approved the definition for reasonable doubt set forth in Redbook instruction No. 2.09.4 See Butler, supra, 646 A.2d at 337. The Redbook instruction on reasonable doubt has been used in this jurisdiction for decades and approved repeatedly, not only by this court but by the D.C. Circuit as well. See, e.g., id.; Foreman, supra note 4, 633 A.2d at 794; Baptist v. United States, 466 A.2d 452, 459 (D.C.1983); Moore v. United States, 120 U.S.App. D.C. 203, 204 & n. 4, 345 F.2d 97, 98 & n. 4 (1965).5 The Supreme Court also has approved some of the definitional terms from the Redbook instruction. See, e.g., Victor, supra, 511 U.S. at 14-15, 114 5.Ct. at 1247 (“An instruction cast in terms of an abiding conviction as to guilt, without reference to moral certainty, correctly states the government’s burden of proof.”); Wilson v. United States, 232 U.S. 563, 570, 34 S.Ct. 347, 349, 58 L.Ed. 728 (1914) (reasonable doubt defined accurately as an ‘(abiding conviction of defendant’s guilt” and a doubt which would cause a juror to “pause and hesitate” before acting in important personal affairs).6 Thus, although arguably not ideal, the Redbook instruction has withstood over time various constitutional challenges.
The Supreme Court has made clear that a constitutionally deficient reasonable doubt instruction is not subject to harmless error analysis and will require reversal. See Sullivan v. Louisiana, 508 U.S. 275, 279-80, 113 S.Ct. 2078, 2081-82, 124 L.Ed.2d 182 (1993) (citation omitted).7 Therefore, a devi*81ation from the instruction in a way which misdescribes or lessens the government’s burden of proof is severely prejudicial to the fairness of the trial and the administration of justice. See Butler, supra, 646 A.2d at 337. For that reason, we have warned that “[e]f-forts to reformulate [the Redbook] instruction should proceed with extreme caution, for ‘[a]n instruction central to the determination of guilt or innocence may be fatally tainted by even a minor variation which tends to create ambiguity.’ ” Foreman, supra note 4, 633 A.2d at 794 (quoting United States v. Alston, 179 U.S.App. D.C. 129, 135, 551 F.2d 315, 321 (1976) (footnote omitted)). In spite of our strong admonitions to the trial court of the unnecessary risks attendant to deviations from the tried and tested Redbook instruction, some judges have modified the language, no doubt in an effort to achieve greater clarity.8 In turn, this has resulted in a number of appeals challenging the deviations as constitutionally deficient. See, e.g., Proctor, supra note 8, 685 A.2d 735, 738 (trial court revised and deleted parts of the Redbook instruction); Butler, supra, 646 A.2d at 335-36 (same); Foreman, supra note 4, 633 A.2d at 794 (trial court substituted different language for phrase “abiding conviction” in Redbook instruction). In the present ease, the trial court abandoned Redbook instruction 2.09 and gave instead one patterned after the FJC instruction on reasonable doubt. See Smith, supra, 687 A.2d at 1359-60 & n. 2.
This case by case approach creates a lack of uniformity on a fundamental principle applicable to every criminal trial. Approval of a standard reasonable doubt instruction, particularly one which eliminates much of the criticism surrounding the current Redbook mstruction, would promote uniformity and avoid the pitfalls of ad hoc interpretations and repetitive constitutional challenges. Adherence to an approved instruction would relieve the appellate court of “the necessities and niceties—and the concomitant uncertainties—of gauging various ... renditions [of the reasonable doubt instruction] in terms of’ their risk of misdescribing the government’s burden of proof. United States v. Thomas, 146 U.S.App. D.C. 101, 110, 449 F.2d 1177, 1186 (1971) (en banc). A standard instruction on this central principle of a criminal trial would thus conserve judicial resources. See Winters v. United States, 317 A.2d 530, 532 (D.C.1974) (en banc).9 Furthermore, “[a]llowing varying definitions ... detracts from the goal of a uniform and equal system of justice.” State v. Portillo, 182 Ariz. 592, 898 P.2d 970, 974 (1995). In a matter central to the determination of guilt or innocence, as this is, the appearance of evenhandedness, like the actuality, is important. “Use of a standard definition thus will eliminate confusion and foster fairness for defendants, the [government], and jurors alike.” Id. At the same time, the approval of a single instruction for use in all criminal trials will not intrude unduly into the area of trial court discretion, for the standard of proof beyond a reasonable doubt is applicable to every criminal trial and is not subject to change because of the evidence or legal theories presented. For all of these reasons, we are persuaded that the approval of a uniform, modified reasonable doubt instruction is appropriate.
II.
The parties in this case and amicus all agree that some modification of the Red-*82book instruction is warranted, although they disagree on its formulation. After reviewing various alternatives, ably presented by the counsel for the parties and amicus curiae, we have formulated an instruction which we believe fairly and accurately conveys the meaning of reasonable doubt and responds to the most substantial criticisms of the Red-book instruction made by some Superior Court judges and by the institutional litigants representing the parties in this case. The instruction retains proven language from the Redbook instruction, but also borrows helpful language from the FJC instruction. The instruction which we adopt is as follows:
The government has the burden of proving the defendant guilty beyond a reasonable doubt. In civil cases, it is only necessary to prove that a fact is more likely true than not, or, in some cases, that its truth is highly probable. In criminal cases such as this one, the government’s proof must be more powerful than that. It must be beyond a reasonable doubt.
Reasonable doubt, as the name implies, is a doubt based upon reason—a doubt for which you have a reason based upon the evidence or lack of evidence in the case. If, after careful, honest, and impartial consideration of all the evidence, you cannot say that you are firmly convinced of the defendant’s guilt then you have a reasonable doubt.
Reasonable doubt is the kind of doubt that would cause a reasonable person, after careful and thoughtful reflection, to hesitate to act in the graver or more important matters in life. However, it is not an imaginary doubt, nor a doubt based on speculation or guesswork; it is a doubt based upon reason. The government is not required to prove guilt beyond all doubt, or to a mathematical or scientific certainty. Its burden is to prove guilt beyond a reasonable doubt.
This instruction maintains the essential concepts required for defining proof beyond a reasonable doubt, but it eliminates expressions from earlier versions of the Redbook instruction which may be viewed as outdated in favor of simpler ones. The formulation “hesitate to act in the graver or more important matters in life,” has been approved by the Supreme Court. See Holland, supra, 348 U.S. at 140, 75 S.Ct. at 137; see also Victor, supra, 511 U.S. at 20-21, 114 S.Ct. at 1250-51.10 The first paragraph is taken from the FJC instruction, with modifications to dispel any claim that jurors will not grasp that the reasonable doubt standard is the highest burden of proof required in a court of law. We have opted to include this language in spite of some suggestion that it introduces legal concepts about civil burdens of proof with which the jurors in criminal trials need not concern themselves. However, even with our one-day/one-trial system, jurors often are called to serve many times and may have had experience on a civil jury. This explanation should serve to avoid any confusion about different standards of proof with which they may be familiar, and at the same time reflect by comparison the very heavy burden of proof required in a criminal trial.
III.
There is ample precedent for the court’s exercise of its supervisory authority to develop a jury instruction to assure fairness and to conserve judicial resources by eliminating uncertainties which result in multiple challenges on appeal.11 Given the great risks to the integrity of the trial which attend a deficient reasonable doubt instruction, the uncertainties and controversies generated by varying definitions, and the importance of fairness and the appearance of fairness in our justice system, the greater part of wisdom would dictate that the trial court give the standard instruction approved here, which has been determined to be faithful to *83the constitutional meaning of reasonable doubt. Therefore, we state, in the strongest terms, that the trial court should “resist the temptation to stray from, or embellish upon, that instruction.” Wills v. State, 329 Md. 370, 620 A.2d 295, 304 (1993)(McAuliffe, J., concurring). As the Supreme Court of New Jersey has stated:
We believe the trial courts will better serve the interest of justice if they do not attempt additional definitions of “reasonable doubt.” ... The failure to adhere to the definition, over objection, runs the risk of reversible error.
State v. Medina, 147 N.J. 43, 685 A.2d 1242, 1252 (1996), cert. denied, — U.S. -, 117 S.Ct. 1476, 137 L.Ed.2d 688 (1997). We adopt this revised uniform instruction prospectively only. See Waits, supra note 11, 362 A.2d at 711.
IV.
Finally, as stated at the outset, the division correctly held that the reasonable doubt instruction given in this ease did not deprive Smith of due process, and our reconsideration en banc does not alter the division’s opinion, which we hereby reinstate. The judgment of conviction is, therefore,
Affirmed.
. Smith was indicted for premeditated first degree murder while armed, but the jury acquitted him on that charge and convicted him of the lesser-included offénse of second degree murder while armed.
. Pursuant to an order of this court, the parties and amicus curiae filed supplemental memoran-da addressing the following questions: (1) whether the court should adopt or approve a uniform instruction on reasonable doubt to replace current standard instruction No. 2.09 from the Redbook; and (2) if so, what that instruction should be.
.The D.C. Circuit has held that trial judges need not define reasonable doubt, and indeed, has expressed the view that “the greatest wisdom may lie with the Fourth Circuit’s and Seventh Circuit’s instruction to leave to juries the task of deliberating the meaning of reasonable doubt.” United States v. Taylor, 302 U.S.App. D.C. 349, 356, 997 F.2d 1551, 1558 (1993); see also United States v. Adkins, 937 F.2d 947, 950 (4th Cir.1991); United States v. Glass, 846 F.2d 386, 387 (7th Cir.1988).
. The standard Redbook instruction now reads:
Reasonable doubt, as the name implies, is a doubt based on reason, a doubt for which you can give a reason. It is such a doubt as would cause [a juror], after careful and candid and impartial consideration of all the evidence, to be so undecided that you cannot say that you are firmly convinced of the defendant’s guilt. It is such a doubt as would cause a reasonable person to hesitate or pause in the graver or more important transactions of life. However, it is not a fanciful doubt, nor a whimsical doubt, nor a doubt based on conjecture. It is a doubt which is based on reason. The government is not required to establish guilt beyond all doubt, or to a mathematical certainty or a scientific certainty. Its burden is to establish guilt beyond a reasonable doubt.
Criminal Jury Instructions for the District of Columbia, No. 2.09 (4th ed.1993). The language "firmly convinced” which appears in the current Redbook edition was substituted for “abiding conviction” which appeared in prior versions after our decision in Foreman, where we encouraged the use of this language taken from the FJC instruction. Foreman v. United States, 633 A.2d 792, 794 (D.C.1993).
. In Moore, the D.C. Circuit Court characterized an instruction essentially identical to the Red-book instruction as "exemplary." Moore, supra, 120 U.S.App. D.C. at 204, 345 F.2d at 98.
. But see note 4, supra, pointing out that "abiding conviction” is no longer part of the Redbook instruction.
. In explaining the reason that a constitutionally deficient reasonable doubt instruction is reviewed differently than other constitutional errors which may be subject to a harmless error analysis under Chapman v. California, 386 U.S. 18, 24, 87 S.Ct. 824, 828, 17 L.Ed.2d 705 (1967), the Supreme Court stated:
Consistent with the jury-trial guarantee, the question [Chapman] instructs the reviewing court to consider is not what effect the constitutional error might generally be expected to have upon a reasonable jury, but rather what effect it had upon the guilty verdict in the case at hand.... The inquiry, in other words, is not whether, in a trial that occurred without the error, a guilty verdict would surely have been rendered, but whether the guilty verdict actually rendered in this trial was surely unattributable to the error. That will be so, because to hypothesize a guilty verdict that was never in fact rendered—no matter how inescapable the findings to support that verdict might be—would violate the jury trial guarantee ....
Since ... there has been no jury verdict within the meaning of the Sixth Amendment, the entire premise of Chapman review is simply absent. There being no jury verdict of guilty-beyond-a-reasonable-doubt, the question *81whether the same verdict of guilty-beyond-a-reasonable-doubt would have been rendered absent the constitutional error is utterly meaningless .... The most an appellate court can conclude is that a jury would surely have found petitioner guilty beyond a reasonable doubt— not that the jury’s actual finding of guilty beyond a reasonable doubt would surely not have been different absent the constitutional error. That is not enough.
Sullivan, supra, 508 U.S. at 279-80, 113 S.Ct. at 2081-82 (citations omitted).
. As observed in Proctor v. United States, 685 A.2d 735, 741 (D.C.1996), underlying these deviations from the Redbook instruction, is a dissatisfaction by trial judges with what seems to them "awkward, archaic, hard-to-comprehend, or misleading [language]” in the standard instruction. (Separate statement of Associate Judge Farrell).
. In Winters, recognizing the recurring problem with an anti-deadlock instruction and the concomitant drain on judicial resources to address the issue, we determined that it would "serve the administration of justice to adopt [an instructional] rule for future cases.” 317 A.2d at 532.
. The current Redbook version reads, "[i]t is such a doubt as would cause a reasonable person to hesitate or pause in the graver or more important transactions of life.”
. See, e.g., Kinard v. United States, 416 A.2d 1232, 1235 & n. 3 (D.C.1980) (determining that falsus in uno instruction would no longer be deemed appropriate in Superior Court); Watts v. United States, 362 A.2d 706, 711 (D.C.1976) (en banc) (adopting a "guilty” and "not guilty” jury instruction); Winters, supra, 317 A.2d at 532 (adopting an anti-deadlock instruction for future cases); see also D.C.Code § 11-102(1995).