208 F.3d 638 (7th Cir. 2000)
United States of America,    Plaintiff-Appellee,v.Jeff Boyd, Charles Green, Sammy Knox,  Noah R. Robinson, and Melvin Mays,    Defendants-Appellants.
Nos. 98-2035, 98-2036, 98-2037, 98-2038 & 98-2060
The  United States Court of Appeals  For the Seventh Circuit
Argued September 27, 1999Decided April 3, 2000

Appeals from the United States District Court  for the Northern District of Illinois, Eastern Division.  No. 89 CR 908--James B. Zagel, Judge. [Copyrighted Material Omitted]
Before Posner, Chief Judge, and Ripple and Rovner,  Circuit Judges.
Posner, Chief Judge.


1
The defendants, members of  Chicago's "El Rukn" street gang, were indicted  along with other members of the gang in 1989 on a  variety of serious federal charges. They were  tried before a jury in 1991 (all but appellant  Mays) and convicted; but the trial judge (Judge  Aspen) ordered a new trial because the government  had knowingly used false testimony to convict  them and had failed to disclose materials that  the defendants could have used to impeach the  government's witnesses. After we affirmed his  order, 55 F.3d 239 (7th Cir. 1995), the  defendants were retried, this time before Judge  Zagel, and at the end of the 12-week trial the  jury again convicted the defendants (now  including Mays) of multiple crimes--mainly  narcotics violations, and murders committed in  the course of turf wars with rival drug gangs--  all pursuant to a continuing and wide-ranging  conspiracy reaching back to the mid-1960s. All  five defendants were sentenced to life  imprisonment except Boyd, who was sentenced to 50  years.


2
The appeals present almost 20 separate issues,  but we confine our discussion to those that have  at least colorable merit. Although all the  appellants are represented by counsel, Robinson  has filed a pro se supplemental brief. Earlier  motions by him to file such a brief were  repeatedly denied. Eventually the presiding judge  of this panel allowed it to be filed; but on  further consideration, given the lateness of the  filing (long after the case was argued), we have  decided to vacate the order allowing the brief to  be filed. It goes without saying that a  represented litigant has no right to file a pro  se brief, e.g., United States v. Gwiazdzinski,  141 F.3d 784, 787 (7th Cir. 1998), and although  we can permit such a filing in appropriate  circumstances, e.g., Hayes v. Hawes, 921 F.2d  100, 101-02 (7th Cir. 1990) (per curiam), given  the lateness of the filing and the repetitive  character of the motion the circumstances are not  appropriate.


3
At the first trial--the one set aside because of  prosecutorial misconduct--Edgar Cooksey was a  defendant and he was convicted with the others.  But after the new trial was ordered, he pleaded  guilty, and he testified for the government at  the second trial. The examination of Cooksey both  by the government's lawyer and by one of the  defense lawyers, which was conducted over a  period of three days, brought out the fact that  Cooksey had been a codefendant of at least some  of the current defendants, that they had been  indicted in 1989, that he had testified at a  previous jury trial in 1991 called "United States  v. Boyd" (which the current jury knew, of course,  was the title of the case it was hearing), that  he had spoken to the judge in that trial in  "allocution" and had "accepted responsibility"  for his acts, that he had pleaded guilty shortly  before the beginning of the current trial, and  that he had been in prison continuously since  1991. The lawyers for the other defendants thrice  objected to the questions that elicited this  information, and moved for a mistrial on the  ground that the jury was bound to infer that the  defendants had been convicted by a previous jury.  The government concedes that it can be a  reversible error to disclose to the jury (or  allow the jury to discover) that a defendant was  previously convicted by another jury, see, e.g.,  United States v. O'Keefe, 722 F.2d 1175, 1179  (5th Cir. 1983); United States v. Attell, 655  F.2d 703, 705-06 (5th Cir. 1981); United States  v. Williams, 568 F.2d 464, 470-71 (5th Cir.  1978), though reversal is not automatic. Patton  v. Yount, 467 U.S. 1025, 1031-35 (1984); United  States v. Keating, 147 F.3d 895, 900 (9th Cir.  1998); cf. United States v. Bruscino, 687 F.2d  938, 940 (7th Cir. 1982) (en banc); United States  v. Plescia, 48 F.3d 1452, 1464-65 (7th Cir.  1995). And reversal is out of the question--no  possible prejudice is shown--if the damning fact  is not actually disclosed. Judge Zagel refused to  grant a mistrial, saying he thought it unlikely  that the jury would infer that the defendants had  previously been found guilty; if he was right,  the question whether the jury could have set  aside their knowledge of the fact would not even  arise.


4
The question of what the jury is likely to have  inferred from statements made in its presence,  like the question whether the jury is likely to  have been prejudiced by hearing things they  shouldn't have, Marshall v. United States, 360  U.S. 310, 312 (1959) (per curiam); United States  v. Bruscino, supra, 687 F.2d at 940-41; United  States v. Zizzo, 120 F.3d 1338, 1349 (7th Cir.  1997), is quintessentially one for the trial  judge to answer, subject only to light appellate  review. Because he has his finger on the pulse of  the trial and monitors the alertness and  attentiveness of the jury, he is in a better  position than the appellate judges to determine  whether prejudicial matter presented at the trial  is likely to have affected the outcome. Judge  Zagel could tell how the jurors seemed to be  "taking" the revelations concerning Cooksey's  previous trial. In the circumstances, we do not  think he abused his discretion in refusing to  grant a mistrial. The revelations had been  scattered over three days of examination and  cross-examination of Cooksey and, since they  employed technical legal terminology (such as  "allocution") and were thus susceptible of other  interpretations by a jury of lay persons, did not  compel an inference that the current defendants  had previously been convicted.


5
The next issue concerns the admissibility of  tape recordings of telephone conversations in  1985 and 1986 in which the defendants made  incriminating admissions. The defendants argue  that the reliability of the recordings was never  adequately determined, that some may have been  tampered with, and that the government violated  the Brady rule by failing to disclose a specific  problem with the accuracy of the tapes that could  have been used to impeach the government's  evidence. Brady v. Maryland, 373 U.S. 83 (1963).  Because tape recordings at once are devastatingly  effective evidence and are susceptible to  tampering that is very difficult to discover,  Title III--the federal statute that regulates  electronic surveillance--requires that recordings  "be done in such way as will protect the  recording from editing or other alterations." 18  U.S.C. sec. 2518(8)(a). To this end, the section  requires that the recordings be judicially sealed  as soon as the interception order pursuant to  which they were made expires. Id.; United States  v. Ojeda Rios, 495 U.S. 257, 263 (1990); United  States v. Jackson, 207 F.3d 910, 915-16 (7th Cir. March 23, 2000); United States v.  Plescia, supra, 48 F.3d at 1463; United States v.  Wong, 40 F.3d 1347, 1375 (2d Cir. 1994). This was  done here, back in 1985 and 1986. The original  recordings were placed in sealed envelopes, and  the envelopes in sealed boxes. Some of the seals,  both on boxes and on envelopes, were later  broken, and anyway the recordings that were  actually placed in evidence were not the original  recordings. They were copies of duplicate  originals made at the same time as the original  recordings and intended to be identical to them.  They differed--or at least were supposed to  differ--only in having been made on a different  machine, recording the same conversations.  Neither the duplicate originals nor the copies  made from them were secured against tampering.


6
The admissibility of the copies was not  challenged at the first trial, and the district  judge ruled that this waived the issue as to all  the appellants but Mays, who was not a defendant  at that trial. The judge was wrong. Rulings made  at a previous trial of the same case only  presumptively control the second trial, under the  doctrine of law of the case, Alston v. King, 157  F.3d 1113, 1116 (7th Cir. 1998), and when the  ruling concerns the admissibility of evidence the  presumption is either nonexistent, Tang v. Rhode  Island, 163 F.3d 7, 11 (1st Cir. 1998); United  States v. Akers, 702 F.2d 1145, 1147-48 (D.C.  Cir. 1983), or weak, Menzer v. United States, 200  F.3d 1000, 1004-05 (7th Cir. 2000); United States  v. Williams, 205 F.3d 23, 34 (2d Cir. Feb.  23, 2000); United States v. Todd, 920 F.2d 399, 403 (6th Cir. 1990); United States v. Birney, 686  F.2d 102, 107 (2d Cir. 1982), since issues of  admissibility are often highly contextual and  evidence at a second trial will often deviate  significantly from that at the first. See, e.g.,  Coal Resources, Inc. v. Gulf & Western  Industries, Inc., 954 F.2d 1263, 1265-66 (6th  Cir. 1992). (The presumption is strongest when  the ruling concerns a rule of law, and some cases  might be taken to suggest that it operates only  then. Arizona v. California, 460 U.S. 605, 618  (1983); Payne v. Churchich, 161 F.3d 1030, 1037  n. 8 (7th Cir. 1998).) Even the Ninth Circuit,  which takes a harder line on the binding effect  of evidentiary rulings made in the first trial,  United States v. Tham, 960 F.2d 1391, 1397-98  (9th Cir. 1991), does not regard failure to  object at the first trial as an irrevocable  waiver. Id. at 1398; United States v. Seidman,  503 F.2d 1027 (9th Cir. 1974). The judge's error  in supposing the defendants absolutely precluded  from challenging the admissibility of the copies  at the second trial was peculiarly harmless,  however, since he had to discuss the merits of  the issue of admissibility with regard to Mays,  and that discussion is equally applicable to the  admissibility of the tape recordings against the  other defendants. And so let us turn to those  merits.


7
The fact that the recordings used at the trial  had not been sealed was not, as the defendants  argue, fatal; nor the fact that the seals had  been broken (the seals have to be broken at some  point, if the recordings are to be placed in  evidence). Neither Title III nor the case law  places specific restrictions on the manner in  which the contents of tape-recorded conversations  can be communicated to the jury at trial. See 18  U.S.C. sec. 2517(3); United States v. Rivera, 153  F.3d 809, 812 (7th Cir. 1998). The relevant  issues are, rather, whether Title III permitted  the disclosure of the contents of the  conversations at all, and whether (if so) the  particular evidence conveying those contents to  the jury was adequately authenticated.


8
The contents of a recorded communication  governed by Title III can lawfully be disclosed  even if the recording was not under seal,  provided the absence of the seal is  satisfactorily explained. 18 U.S.C. sec.  2518(8)(a); cf. United States v. Jackson, supra,  at 915-16. The usual satisfactory explanation is a  judicial order unsealing the recording so that it  can be used in evidence, and such orders were  indeed issued here for both sets of tapes that  are at issue. In the case of successive trials,  as we have here, the recording should be resealed  after the first trial, United States v. Long, 917  F.2d 691, 699-700 (2d Cir. 1990); United States  v. Scopo, 861 F.2d 339, 347 (2d Cir. 1988)--and  promptly, too. But this was done. Although  defendants argue--belatedly, in their reply  brief, Employers Ins. of Wausau v. Browner, 52  F.3d 656, 665-66 (7th Cir. 1995)--that one set of  tapes had been unsealed for the nine years since  the first trial, the trial judge was entitled to  and did credit the contrary testimony of the  government agent who examined them in preparation  for the second trial.


9
But it is not the case that these recordings  were merely removed from the boxes and envelopes  pursuant to judicial order and played to the  jury; they were not played to the jury at all;  copies were played to the jury and the second and  separate issue concerning their admissibility is  whether the copies were adequately authenticated.  On this issue two types of evidence were  presented that the judge found convincing. First,  one of the turncoat witnesses, Jackie Clay,  testified that a recording of a telephone  conversation that he had participated in back in  1986 was accurate. Although testifying ten years  later Clay could hardly have been certain about  the matter--any pretense of certainty would  merely have cast doubt on his credibility--  participants in other recorded conversations who  testified for the government were not asked by  the defendants' lawyers whether the recordings  were accurate. The district judge inferred from  testimony by government agents that the other  conversations had been recorded in like manner to  the one Clay testified about and, from the  absence of any contrary evidence, that the  recordings of those conversations were probably  accurate too. Second, a government agent  testified that he opened some of the sealed  evidence envelopes pursuant to an unsealing order  by the district judge and compared the tapes in  them to the tapes played at trial, and found no  discrepancies.


10
Clay's testimony was weak because of the lapse  of time. The agent's was stronger, although not  airtight. For one thing, he didn't compare all  the tapes played at trial with the originals.  Rather, he conducted a spot check, and having  discovered no discrepancies in the tapes that he  sampled decided not to check further. For  another, there is an unexplained discrepancy  between one of the original recordings and its  duplicate original, which although supposed to be  identical contained conversations not audible on  the original. The expert who examined the two  tapes could not determine the cause of the  discrepancy. It could have been a malfunction, or  it could have been a bit of creative editing, but  the latter inference, as the judge determined,  was the less likely, precisely because the  duplicate contained more conversation than the  original. It was the duplicate that was used in  evidence, and if the government had edited out  portions that favored the defendants, the  original would have had more conversation than  the duplicate. Although it is possible in  principle that the government "edited in"  additional conversation to the duplicate, there  is no indication at all of this more elaborate  form of tampering. Similarly, while it would have  been preferable had the agent checked all the  tapes, no reasons have been suggested for  doubting either the good faith or the adequacy of  his sampling.


11
It is essential to distinguish between excluding  evidence for want of adequate authentication, and  challenging its weight. The defendants were  entitled to and did question the weight that the  jury should give the tape recordings in light of  the possibility of tampering, but questions of  authentication are governed by Fed. R. Evid.  901(a), which merely requires "evidence  sufficient to support a finding that the matter  in question is what its proponent claims," that  is, that the recordings played to the jury were  in fact recordings of the defendants'  conversations. Testimony by an "ear" witness,  such as Clay, is sufficient, United States v.  Brown, 136 F.3d 1176, 1182 (7th Cir. 1998); there  is more here; and we have said in previous cases  that only in "extraordinary" circumstances will  we reverse the trial judge's decision to admit  tape recordings over objections based on lack of  authentication. United States v. Magana, 118 F.3d  1173, 1207 (7th Cir. 1997); United States v.  Welch, 945 F.2d 1378, 1383 (7th Cir. 1991);  United States v. Vega, 860 F.2d 779, 788 (7th  Cir. 1988). That high standard is not met here.


12
The Brady rule requires the government to  disclose evidence it knows about that would be  helpful to the defense, whether because the  evidence is exculpatory or because it could be  used to impeach the government's evidence. Brady  v. Maryland, supra, 373 U.S. at 87; Strickler v.  Greene, 119 S. Ct. 1936, 1948 (1999). The  discrepancy between one of the original tapes and  its duplicate, a discrepancy that could have been  used to some effect to impeach the government's  taped evidence, may have arisen as early as 1986,  when the two recordings were made; in any event  it was not recent, and the defendants ask us to  infer from this that the government must have  known about it. But of this there is no other  evidence and the inference is implausible because  the government prepared its case from the  duplicate originals while the "original  originals" remained in storage. So far as  appears, the discrepancy was first discovered by  the defendants, who thought they heard something  odd on one of the tapes; they drew this to the  judge's attention and then the comparison was  conducted, which confirmed the existence of the  anomaly. Brady liability is not strict; the  government does not violate Brady by failing to  disclose information that it (or its agents,  e.g., Kyles v. Whitley, 514 U.S. 419, 437 (1995)-  -a category that doesn't include the criminal  defendants whom it prosecutes!) doesn't know  about. United States v. Bhutani, 175 F.3d 572,  577 (7th Cir. 1999); United States v. Earnest,  129 F.3d 906, 910 (7th Cir. 1997); United States  v. Avellino, 136 F.3d 249, 255 (2d Cir. 1998).  The discrepancy between the tapes is such  information.


13
We come last to the most troubling issue in the  case--whether Judge Zagel should have  disqualified himself from presiding at this  trial. We have already held, in another case  involving the El Rukns, that Judge Zagel's  refusal to disqualify himself was not a plain  error, United States v. Franklin, 197 F.3d 266,  270 (7th Cir. 1999), but the question remains  whether it was error. There is a threshold  procedural question, which is both novel and  unnecessary to resolve. Section 144 of the  Judicial Code entitles a party to disqualify a  judge (only once per case, however) on the basis  just of an affidavit sufficiently alleging the  existence of a personal bias or prejudice in  favor of an adverse party or against the affiant;  but the affidavit must be "accompanied by a  certificate of counsel of record stating that it  is made in good faith." Defendant Robinson filed  a section 144 affidavit against Judge Zagel, but  without the required certificate, because  Robinson was proceeding pro se. The judge ruled  that the absence of the certificate was fatal.  The ruling denies pro se parties the benefit of  the statute, a result that might be thought an  undue burden on the constitutional right of a  criminal defendant to proceed pro se. Faretta v.  California, 422 U.S. 806, 834, 836 (1975); United  States v. Brock, 159 F.3d 1077, 1079 (7th Cir.  1998); see also 28 U.S.C. sec. 1654. Yet the  requirement of the certificate is salutary, given  that the statute makes the party's affidavit  conclusive for recusal provided it alleges the  requisite bias or prejudice. The obvious  solution, suggested by Robinson himself but  opposed by the government and rejected by the  judge, is to appoint a lawyer for the pro se  defendant for the limited purpose of enabling him  to determine whether to file the certificate. The  rejection of this measure--a measure we commend  to the district courts in future cases--turns out  to have been harmless, however, because the  relevant facts in Robinson's affidavit were  conceded.


14
Section 455(a) of the Judicial Code requires a  judge to disqualify himself "in any proceeding in  which his impartiality might reasonably be  questioned." Our cases hold that appellate review  of a judge's refusal to disqualify himself under  this section is possible only by petitioning the  appellate court for mandamus before trial. E.g.,  In re Hatcher, 150 F.3d 631, 637 (7th Cir. 1998);  United States v. Horton, 98 F.3d 313, 316-17 (7th  Cir. 1996); Taylor v. O'Grady, 888 F.2d 1189,  1201 (7th Cir. 1989); United States v.  Balistrieri, 779 F.2d 1191, 1204-05 (7th Cir.  1985). This is a minority position, see, e.g., In  re Cargill, Inc., 66 F.3d 1256, 1264 and n. 10  (1st Cir. 1995); United States v. Cooley, 1 F.3d  985, 996 n. 9 (10th Cir. 1993); In re School  Asbestos Litigation, 977 F.2d 764, 777 n. 12 (3d  Cir. 1992); Chitimacha Tribe v. Harry L. Laws  Co., 690 F.2d 1157, 1164 n. 3 (5th Cir. 1982),  but the defendants do not ask us to reexamine it.  On the contrary, they expressly waive any  challenge to the rule by stating in their  consolidated brief that "the motion for recusal  under 28 U.S.C. sec. 455(a) could only be, and  was, appealed by mandamus." Given this express  waiver by experienced counsel, it would be  inappropriate for us to reexamine the rule in  this case.


15
Because the rule forecloses appellate review at  the conclusion of the case, we review a petition  for mandamus to enforce section 455(a) under the  normal appellate standard. Hook v. McDade, 89  F.3d 350, 353-54 and n. 3 (7th Cir. 1996). Such a  petition was filed here, and another panel of  this court denied it, but in an unpublished order  with no statement of reasons, a disposition that  we find puzzling because, as will soon become  clear, the case for disqualification under  section 455(a) was more than colorable, and  indeed in our judgment was compelling. But there  is no reason to suppose that the panel which  denied mandamus applied the incorrect standard,  and in the absence of such an error we cannot  revisit the issue without abandoning the rule  that makes mandamus the exclusive route for  challenging a judge's refusal to disqualify  himself under section 455(a).


16
The defendants also argue, however, that Judge  Zagel should have disqualified himself under  either of two other subsections (or both) of  section 455. The first is (b)(1), which so far as  bears on this case requires disqualification if  the judge has "personal knowledge of disputed  evidentiary facts concerning the proceeding." The  second is (b)(3), which requires disqualification  if the judge had, when he was a government  employee, "participated as counsel, adviser or  material witness concerning the proceeding or  expressed an opinion concerning the merits of the  particular case in controversy."


17
In 1983, at which time the now-Judge Zagel was  the head of the Illinois state police, Robinson  opened a restaurant in Chicago. Late in 1985 or  early in 1986, when Zagel was still head of the  state police, Robinson hired security guards for  his restaurant from a company called Security &  Maintenance Service (SMS), which was owned and  operated by El Rukn "General" Hunter, a key  government witness at the 1996 trial here on  appeal. These guards were unarmed but SMS had  applied for a license that would permit them to  be armed. The El Rukns' purpose in operating a  security agency whose employees were authorized  to carry weapons was, of course, to strengthen  the gang's position in the endless turf wars in  the course of which the murders with which these  defendants were charged were committed. The  authorities got wind of the scheme. They were  already investigating the El Rukns (whose drug  and related criminal activities went back to the  1960s, remember) by means of a joint federal,  state, and local task force that included members  of the Illinois state police. The task force  conducted a "sting" of SMS. An Illinois state  police officer played a key role in the sting,  operating undercover and dealing directly with  Hunter and Robinson. In June of 1986, Chicago  police officers who were members of the task  force and who later worked on the present case  raided SMS's premises, which Robinson owned, and  arrested (at another location) 18 of its  employees. One of them, Crowder, was a defendant  in the first trial of this case and a defense  witness in the second trial, the trial before  Judge Zagel.


18
The day of the arrest, Director Zagel held a  joint press conference with Richard Daley, at the  time the Cook County prosecutor. They announced  the arrests and explained that they had begun  investigating SMS when they learned that Crowder,  an El Rukn "captain," had applied for a state  firearm identification card. Zagel remarked that  "street gangs [such as the El Rukns] have grown  to rival organized crime in the scope of their  operations, and in the savagery in which they  control entire sections of the city." The El  Rukns task force produced the evidence that led  to the 1989 indictments of the present  defendants. Not only did two of the El Rukns who  had been involved in the SMS caper testify at the  trial before Judge Zagel, but they testified--  Hunter extensively--about the caper, using it to  tie Robinson to other El Rukn activities as well.


19
In denying the motion to recuse, Judge Zagel  said that the SMS investigation had had nothing  to do with the current trial, but this is  incorrect. The creation of SMS was part of the  drug and incidental murder conspiracy for which  the defendants in the present case were tried and  convicted before Judge Zagel, although SMS's  activities were not charged as overt acts of the  conspiracy. The judge was involved in the  investigation of activities at issue in the  trial, and the press conference shows that he had  personal, extrajudicial knowledge of those  activities. But SMS's activities were not at  issue in this case except insofar as they  connected Robinson to the El Rukns. Had Judge  Zagel learned of this connection from the 1986  investigation of SMS, Robinson would be entitled  to a new trial before a different judge. But  Zagel did not mention Robinson at the press  conference, and there is no basis in the record  for Robinson's claim that Zagel was the "point  man" for the investigation and had "full  knowledge" of its details. The judge denied this  charge on the record, and in the absence of  contrary evidence (Robinson's mere assertion not  being evidence), we must credit the denial.  United States v. Balistrieri, supra, 779 F.2d at  1202.


20
This conclusion is only superficially in tension  with our (and Judge Zagel's) crediting the facts  alleged in Robinson's affidavit in support of his  motion to recuse Judge Zagel under 28 U.S.C. sec.  144. The only facts in such an affidavit that  must be credited, and plainly the only facts in  Robinson's affidavit that Judge Zagel did credit,  are those that are "sufficiently definite and  particular to convince a reasonable person that  bias exists; simple conclusions, opinions, or  rumors are insufficient." United States v. Sykes,  7 F.3d 1331, 1339 (7th Cir. 1993); see also  United States v. Balistrieri, supra, 779 F.2d at  1199; Jones v. Pittsburgh Nat'l Corp., 899 F.2d  1350, 1356 (3d Cir. 1990); 13A Charles Alan  Wright, Arthur R. Miller & Edward H. Cooper,  Federal Practice and Procedure sec. 3551, pp.  634-37 (2d ed. 1984). Robinson's assertions that  Zagel was the "point man" of the investigation  and had "full knowledge" of the details of the  investigation don't count as factual assertions;  they are conclusions.


21
Section 455(b)(3) is also inapplicable. Zagel  did not participate other than as judge in the  present case and did not, back when he was head  of the state police, express an opinion about it.  The case was then, of course, years in the  future. There is a pregnant difference in wording  between the participation and expression-of-  opinion clauses of 455(b)(3). The former refers  to participation in "the proceeding," the latter  to expressing an opinion on the merits of "the  particular case in controversy," and we have held  that the use of the word "particular" narrows the  clause to the situation in which the judge  expressed his opinion in "the present case, not a  related former case." Russell v. Lane, 890 F.2d  947, 948 (7th Cir. 1989); cf. Rice v. McKenzie,  581 F.2d 1114, 1116 (4th Cir. 1978). In any  event, since nothing Zagel said at the press  conference could reasonably be construed as an  expression of opinion on the merits of the case  that he presided over, we need not pursue this  novel and interesting interpretive question.


22
The cases interpreting the participation clause  do not require a formal identity between the  proceeding in which the government employee who  is now a judge participated or expressed an  opinion about; it is enough if they overlap  significantly. See, e.g., United States v.  Outler, 659 F.2d 1306, 1312-13 (5th Cir. 1981);  Jenkins v. Bordenkircher, 611 F.2d 162, 166 (6th  Cir. 1979); Mixon v. United States, 608 F.2d 588,  591-92 (5th Cir. 1979). And there was an overlap  here, in the part of the SMS investigation that  linked Robinson to the El Rukns. But Director  Zagel never expressed an opinion about that  aspect of the investigation, and the requisite  "participation" is not imputed to a supervisor by  virtue of his supervisory authority; it must be  personal, and it was not. E.g., Mangum v.  Hargett, 67 F.3d 80, 83 (5th Cir. 1995); Kendrick  v. Carlson, 995 F.2d 1440, 1444 (8th Cir. 1993);  United States v. Di Pasquale, 864 F.2d 271, 279  (3d Cir. 1988). The exception noted in the last-  two cited cases for where the supervisor is the  U.S. Attorney is not applicable here.


23
Recurring briefly to section 455(a), we wish to  emphasize our belief that compliance with it is  essential to the perceived legitimacy of the  judicial process, especially when the defendants  are vicious criminals facing long sentences and  the prosecution has been marred by  irregularities. It would have been far, far  better for Judge Zagel to have recused himself in  light of his earlier involvement with the  parallel proceeding against the El Rukns and the  fact that two of the El Rukns involved in that  proceeding testified in the present case. But the  panel that considered the petition for mandamus  ruled that there was no violation of section  455(a), and while we disagree with the ruling,  the issue of its soundness is not before us.


24
Several sentencing issues remain to be  discussed. Green and Mays argue that their  sentences violate the ex post facto clause, U.S.  Const., art. I, sec. 9, cl. 3, because the  conspiracies did not persist beyond the date on  which the statutes under which they were  sentenced were enacted or because they had  withdrawn from the conspiracies prior to that  date. The first claim is just wrong, for although  there wasn't a great deal of evidence of  continued drug dealing by the El Rukns subsequent  to the crucial dates (November 1, 1987, for one  of the statutes under which these defendants were  sentenced and November 18, 1988, for another),  there was enough to place the district judge's  finding beyond possibility of reversal for clear  error. Withdrawal from a conspiracy requires a  definitive break, rather than mere cessation of  activities even when combined with a subjective  determination not to resume; otherwise a  conspirator could sit back and wait to see  whether the conspiracy had succeeded or failed  and only then decide whether to announce that he  had withdrawn. E.g., United States v. Wilson, 134  F.3d 855, 863 (7th Cir. 1998); United States v.  Williams, 81 F.3d 1434, 1442 (7th Cir. 1996);  United States v. Diaz, 176 F.3d 52, 98 (2d Cir.  1999). Mays's argument that he withdrew when he  became a fugitive from justice borders on the  frivolous, United States v. Pandiello, 184 F.3d  682, 687 (7th Cir. 1999), as it would merely  reward fugitives; and anyway there is nothing  about hiding to suggest withdrawal--Mays was  hiding from the police rather than from the El  Rukns.


25
Green has a better argument, that he could not  be given a sentencing enhancement for having been  a leader of the conspiracy (U.S.S.G. sec.  3B1.1(a)) when his leadership role had--and this  the government acknowledges--ended with his  demotion from El Rukn "General" to private before  the guideline under which his sentence was  enhanced went into effect (as one of the original  guidelines) on November 1, 1987. The conspiracy  of which he was a member straddled the date of  promulgation, and a crime that straddles can be  punished under a guideline promulgated after the  straddle date. E.g., United States v. Kramer, 955  F.2d 479, 485 (7th Cir. 1992); United States v.  Hargus, 128 F.3d 1358, 1365 (10th Cir. 1997), and  United States v. Smith, 46 F.3d 1223, 1239 (1st  Cir. 1995). The straddle rule implies punishment  for conduct committed before the date of the  guideline that determined the severity of the  punishment, and we cannot see what difference it  can make whether the pre-guideline conduct was  the sale of a quantity of drugs perhaps much  greater than any that occurred after the critical  date or the exercise of leadership  responsibilities relinquished by that date.


26
Green's best case is United States v. Torres,  901 F.2d 205, 226-27 (2d Cir. 1990), which held  that the ex post facto clause forbids punishing  the defendants as "principal administrators,  organizers, or leaders" of a continuing criminal  enterprise if their leadership role did not  continue after the enactment of the statute  creating the offense, even though the enterprise  itself did continue past that date. See also  United States v. Williams-Davis, 90 F.3d 490,  510-11 (D.C. Cir. 1996) (acknowledging but  distinguishing Torres). The statute at issue in  Torres created a new substantive offense that  required as one of its elements that the  defendant have had a leadership role, and so  punished Torres for engaging in conduct before  the statute was passed. In our case the defendant  committed all the elements of the offense after  the change in the sentencing guideline and by  doing so became responsible for the conduct in  which he had engaged before the change. Torres  was not a straddle case; ours is; if the  difference seems tenuous, then we must reject  Torres, as we are committed to the straddle  doctrine--and so, for that matter, is the Second  Circuit, which reaffirmed the straddle doctrine  in Torres itself. We add that Green could have  avoided the new guideline by quitting the  conspiracy when the guideline was announced but  before it took effect.


27
Last, we note some clerical mistakes in the  judgments. Mays's judgment should reflect a  guidelines life sentence on count 3 and 60 months  on count 4, rather than vice versa, and Green's  judgment should reflect a life sentence on counts  1 and 3 and concurrent 10-year terms on counts 4  and 5, rather than a life sentence on counts 1,  4, and 5 and a 10-year sentence on count 3. As  modified to correct these mistakes, the judgments  are


28
Affirmed.


29
RIPPLE, Circuit Judge, dissenting.


30
The panel is  unanimous in its view that the trial judge should  have recused himself under sec. 455(a), which  requires a judge to "disqualify himself in any  proceeding in which his impartiality might  reasonably be questioned." Under the  circumstances set forth in detail by the majority  here, in any other circuit a new trial would be  ordered. In this circuit, however, we can only  review the trial judge's decision against recusal  when the issue is presented in a petition for a  writ of mandamus. The defendants did file a  petition for mandamus relief from the trial  judge's decision not to recuse himself, and  another panel of this court denied that petition  without opinion.


31
The rule that mandamus is the only avenue by  which a party can seek review of a ruling under  sec. 455(a) is well-established in this circuit.  See United States v. Horton, 98 F.3d 313, 316-17  (7th Cir. 1996); Hook v. McDade, 89 F.3d 350, 353  n.2 (7th Cir. 1996); United States v. Towns, 913  F.2d 434, 443 (7th Cir. 1990). This circuit's  view has been that sec. 455(a) is intended to  protect against the appearance of impropriety,  and that, once the proceedings in the district  court have been completed, the harm sec. 455(a)  seeks to prevent has already occurred. See United  States v. Troxell, 887 F.2d 830, 833 (7th Cir.  1989). Thus, we have required litigants to bring  mandamus petitions to cure potential problems  under sec. 455(a) and to prevent a potentially  tainted trial from ever taking place. See id.


32
No other court of appeals has followed our  approach. See Kenneth M. Fall, Note, Liljeberg v.  Health Services Acquisition Corp.: The Supreme  Court Encourages Disqualification of Federal  Judges Under Section 455(a), 1989 Wis. L. Rev.  1033, 1056. Some circuits have rejected  explicitly our position. The Third Circuit has  said that mandamus is the preferred method of  appeal, but allows review on direct appeal  because it may provide a "partial cure" to any  harm to the public perception of the judiciary.  See In re School Asbestos Litig., 977 F.2d 764,  777 n.12 (3d Cir. 1992). The Tenth Circuit has  held that, although sec. 455(a) is concerned with  the rights of the public, the parties do retain  some rights thereunder, and direct appeal may  therefore be appropriate. See United States v.  Cooley, 1 F.3d 985, 996 n.9 (10th Cir. 1993).  Other circuits have entertained sec. 455(a)  arguments on direct appeal and, indeed, have  addressed the merits or found the issue waived  because it was not raised in the district court.  See, e.g., United States v. Mosby, 177 F.3d 1067,  1068-69 (8th Cir. 1999); United States v.  Morrison, 153 F.3d 34, 48-49 (2d Cir. 1998);  United States v. Barrett, 111 F.3d 947, 951-53  (D.C. Cir. 1997); United States v. Sturman, 951  F.2d 1466, 1481-82 (6th Cir. 1991); Diversified  Numismatics, Inc. v. City of Orlando, 949 F.2d  382, 384-85 (11th Cir. 1991) (per curiam); United  States v. Arache, 946 F.2d 129, 140 (1st Cir.  1991); United States v. Payne, 944 F.2d 1458,  1476-77 (9th Cir. 1991); United States v. Wade,  931 F.2d 300, 302-05 (5th Cir. 1991); United  States v. Mitchell, 886 F.2d 667, 671 (4th Cir.  1989).


33
Moreover, we not only stand alone among the  circuits in our approach to this question, but we  also have taken a position in considerable  tension with the decisions of the Supreme Court  of the United States. Indeed, the Supreme Court  appears to have taken a different path. Although  the Court has not rejected explicitly that  mandamus is the only avenue of review for sec.  455(a) matters, it has twice interpreted that  section in cases brought to it in the manner of  an appeal from final judgment. See Liteky v.  United States, 510 U.S. 540 (1994); Liljeberg v.  Health Services Acquisition Corp., 486 U.S. 847  (1988). These cases, especially Liljeberg's  approval of vacatur of a trial court's judgment,  clearly cast significant doubt on our view that  mandamus is the only appropriate remedy under  sec. 455(a). Nevertheless, we never have  considered whether these decisions of the Supreme  Court make our approach untenable; we have  continued to follow our same approach even after  the announcement of those Supreme Court  decisions.


34
This case points out one of the pitfalls of our  approach. As the Third Circuit has suggested, a  trial judge well might appear unbiased at the  outset of a trial, but later events might cause a  judge's impartiality to be reasonably questioned  and thus make appropriate the "partial cure" of  reversing the improperly obtained verdict.  Asbestos Litig., 977 F.2d at 777-78. Indeed, in  one recent case, the First Circuit, although  denying mandamus relief, specifically left open  the possibility that further development of the  record could lead to a different conclusion on an  appeal from final judgment. See In re Martinez-  Catala, 129 F.3d 213, 221 (1st Cir. 1997).  Regardless of whether this panel would have  issued the same ruling as the earlier motions  panel if it had been presented with the record  available at that early stage of the litigation,  the record made at trial has convinced us that  recusal is necessary. There must be public  confidence in a judgment that incarcerates  defendants, in some cases for the rest of their  lives. The trial of this matter was a difficult  task. It required that the trial court make many  rulings, both with respect to the admissibility  of evidence and the enhancement of sentences,  that required the exercise of a great deal of  discretion.


35
After thorough review of the record, this panel  believes that the district judge should have  recused himself under 28 U.S.C. sec. 455(a). Only  our rigid adherence to a procedural rule not  followed in any other circuit and in significant  tension with the decisions of the Supreme Court  of the United States prevents our giving the  relief that, under the prevailing national  standards, would be granted. See, e.g., United  States v. Bremers, 195 F.3d 221 (5th Cir. 1999)  (vacating conviction because trial judge should  have recused himself under sec.455(a)); Cooley, 1  F.3d at 998 (same); United States v. Brown, 539  F.2d 467 (5th Cir. 1976) (same). See also United  States v. Waskom, 179 F.3d 303, 315-16 (5th Cir.  1999) (vacating sentence in guilty plea case even  in the absence of specific allegation of  sentencing error because trial judge should have  recused himself); United States v. Reyes, 160  F.3d 258, 259 (5th Cir. 1998) (vacating sentence  in guilty plea case because of failure to  recuse).


36
The majority characterizes the defendants'  reference to the earlier mandamus proceeding as a  waiver of the argument that mandamus should not  be the only available remedy. The defendants  state: "Defendants appeal the denial of recusal  under 28 U.S.C. sec.sec. 144 and 455(b). The  motion for recusal under 28 U.S.C. sec. 455(a)  could only be, and was, appealed by mandamus."  Appellant's br. at 49. This was sufficient to put  this court on notice of our rule that only  mandamus relief is available under sec. 455(a).  It is indeed a parsimonious reading of this  statement to characterize it as a knowing and  intelligent waiver. Far from ignoring the issue,  the defendants specifically brought it to our  attention. Because the defendants raised the  matter, and clearly have maintained throughout  this litigation that recusal under sec. 455(a)  was required, this court should not be restrained  from reconsidering in this case our position on  the issue.1


37
Moreover, even if the defendants did not raise  this issue, we are in no way precluded from  raising it on our own in the interests of  justice. The Supreme Court has acknowledged that  it often decides cases on issues other than those  argued fully by the parties:


38
"On a number of occasions, this Court has  considered issues waived by the parties below and  in the petition for certiorari because the issues  were so integral to decision of the case that  they could be considered 'fairly subsumed' by the  actual questions presented." Gilmer v.  Interstate/Johnson Lane Corp., 500 U.S. 20, 37,  111 S. Ct. 1647, 114 L.Ed.2d 26 (1991) (Stevens,  J., dissenting) (citing cases). The court has not  always confined itself to the set of issues  addressed by the parties.


39
Kolstad v. American Dental Assoc., 119 S.Ct.  2118, 2127 (1999). The Court has also  specifically instructed the courts of appeals  that they, too, may raise issues on their own  initiative:


40
The matter of what questions may be taken up and  resolved for the first time on appeal is one left  primarily to the discretion of the courts of  appeals, to be exercised on the facts of  individual cases. We announce no general rule.  Certainly there are circumstances in which a  federal appellate court is justified in resolving  an issue not passed on below, as where the proper  resolution is beyond any doubt, or where  injustice might otherwise result.


41
Singleton v. Wulff, 428 U.S. 106, 121 (1976)  (citations and quotations omitted); see also  Niedert v. Rieger, 200 F.3d 522, 527 (7th Cir.  1999) (quoting Singleton); United States v.  Brown, 739 F.2d 1136, 1145 (7th Cir. 1984)  (same).


42
Prior to Singleton, the Ninth Circuit explained  the circumstances that might motivate a court of  appeals to address a matter without the benefit  of full briefing by the parties:


43
There is . . . no rigid and undeviating  judicially declared practice under which courts  of review invariably and under all circumstances  decline to consider all questions which have not  previously been specifically urged. Indeed there  could not be without doing violence to the  statutes which give federal appellate courts the  power to modify, reverse or remand decisions as  may be just under the circumstances. Exceptional  cases or particular circumstances may prompt a  reviewing court, where injustice might otherwise  result or where public policy requires, to  consider questions neither pressed nor passed  upon below.


44
Nuelsen v. Sorensen, 293 F.2d 454, 462 (9th Cir.  1961) (citation and quotationsomitted).2 As we  did in Niedert and Brown, and as the Ninth  Circuit did in Nuelsen, so too have other  circuits acknowledged that they may, when justice  requires it, raise critical issues of law sua  sponte.3 The Ninth Circuit wisely cautioned  that this power must be "exercised sparingly."  Nuelsen, 293 F.2d at 462. This case, however, is  the sort of exceptional case that casts new light  on procedures previously taken for granted.


45
If we may sua sponte raise and decide  substantive questions of law, then surely we have  the power to sua sponte alter the procedures we  ask litigants to follow in their efforts to seek  resolution of their substantive questions of law.  It is well settled that stare decisis has less  effect in the context of procedural rules, which  do not serve as a guide to lawful behavior. See  Hohn v. United States, 524 U.S. 236, 251-52  (1998); United States v. Gaudin, 515 U.S. 506,  521 (1995).


46
The prosecution of the El Rukn crime  organization has been a deeply troubling episode.  Chief Judge Aspen presided over the first trial  of this particular case, and, in ordering a  retrial, described the situation as tragic,  noting that the prosecutorial misconduct in the  case had wasted years of hard work by the courts,  prosecutors, and law enforcement officers. See  United States v. Boyd, 833 F. Supp. 1277, 1281  (N.D. Ill. 1993), aff'd, 55 F.3d 239 (7th Cir.  1995). Two other El Rukn trials were also  declared mistrials. See United States v. Andrews,  824 F. Supp. 1273 (N.D. Ill. 1993); United States  v. Burnside, 824 F. Supp. 1215 (N.D. Ill. 1993).  As the judiciary was quick to correct an abuse of  power in another branch of government after the  first trial, it also ought to be willing to  correct an error in its own house--even one made  in good faith--so that the public can have  confidence that, even in the most notorious of  criminal cases, the evenhandedness of the  judicial process is above reproach.


47
It is time for us to join the rest of the  Country and permit review by appeal of a failure  to recuse under sec. 455(a). I would vacate the  judgments of conviction and order a new trial.



Notes:


1
 When a party does not make a fully formed  argument that we should overrule our earlier  precedent to align ourselves with other courts,  the court may consider the argument waived. See  United States v. Martin, 195 F.3d 961, 967 (7th  Cir. 1999). Waiver is not mandatory, of course,  but instead, appellate courts have the discretion  to find that arguments are waived. See, e.g.,  Smith v. Freeman, 892 F.2d 331, 337 n.12 (3d Cir.  1989) (collecting cases). We are therefore under  no obligation to avoid this question.


2
 See also All Care Nursing Serv., Inc. v. Bethesda  Mem. Hosp., 887 F.2d 1535, 1538 n.3 (11th Cir.  1989) (quoting Nuelsen); Boals v. Gray, 775 F.2d  686, 691 (6th Cir. 1985) (same); Cohen v. West  Haven Bd. of Police Comm'rs, 638 F.2d 496, 500  n.6 (2d Cir. 1980) (citing Nuelsen); McKissick v.  United States, 379 F.2d 754, 759 (5th Cir. 1967)  (quoting Nuelsen).


3
 See Curry v. Beatrice Pocahontas Coal Co., 67  F.3d 517, 522 n.8 (4th Cir. 1995) ("The normal  rule of course is that the failure to raise an  issue for review in the prescribed manner  constitutes a waiver. But the rule is not an  absolute one and review may proceed (even  completely sua sponte) when the equities  require." (citation omitted)); Lambert v. Genesee  Hosp., 10 F.3d 46, 56 (2d Cir. 1993) ("However,  we have discretion to consider and decide sua  sponte a dispositive issue of law."); Counts v.  Kissack Water & Oil Serv., Inc., 986 F.2d 1322,  1325-26 (10th Cir. 1993) ("Although it is rarely  done an appellate court may, sua sponte, raise a  dispositive issue of law when the proper  resolution is beyond doubt and the failure to  address the issue would result in a miscarriage  of justice.").


