David Bianehini appeals from his conviction after a jury trial in the District Court for the District of Vermont, Franklin S. Billings, Chief Judge, and from the resulting sentence of 250 months imprisonment *47for conspiracy to manufacture marijuana, for possession of marijuana with intent to distribute, and for interstate travel in furtherance of illegal activity. 759 F.Supp. 1081 (D.Vt.1991). He contends that the district court’s rulings regarding third-party contact with a juror denied him the right to trial by an impartial jury, that failure to instruct the jury on the consequences of a verdict of not guilty by reason of insanity constituted error, and that the district court incorrectly calculated the weight of marijuana involved for purposes of applying the sentencing guidelines. We affirm the conviction and remand for resentenc-ing.
It is uncontested that David Bianchini and his co-conspirators operated two highly sophisticated marijuana farms in Vermont, one in Glover, the other in West Charleston. Police searches uncovered elaborate indoor farms with specially tailored climate control and lighting equipment and approximately 3700 mature marijuana plants. Bianchini’s arrest followed.
On August 30, 1990, a grand jury returned a five-count indictment against Bianchini and his co-conspirators,1 charging them with manufacturing, possessing and distributing marijuana, with conspiracy to manufacture, possess and distribute marijuana, and with interstate travel in furtherance of illegal activity. At trial, Bianchini did not contest the charges, but instead offered an insanity defense based on his experiences in the Vietnam War.
During the trial, one of the jurors, Arthur Tenner, informed Judge Billings that he had received a telephone call from an unidentified man, offering him $5,000 to secure a mistrial. The judge allowed Tenner to remain on the jury while the F.B.I. investigated the matter.2 He instructed Tenner not to discuss the call with other members of the jury or anyone else outside the investigation.
After two days of testimony, the trial stood adjourned for Thanksgiving recess. Over the weekend, Tenner received a note threatening his life. On the following Monday, Tenner reported to Judge Billings that he could not remain impartial, and the judge dismissed him from the jury. At that time, the judge informed trial counsel about the events involving Tenner and indicated that he would conduct a voir dire of the jury panel. Neither party objected.
When questioned, the remaining jurors indicated that they had not been approached by any third party, but two jurors said they had spoken to Tenner about the case. When Judge Billings examined these jurors in chambers, they told him that Tenner had made some disparaging remarks about Bianchini’s insanity defense. Neither juror, however, appeared to know anything about the attempted bribe, and both assured the judge that they could remain impartial. This voir dire was conducted in the presence of counsel, and.neither party objected or asked for a mistrial.
After the jury returned a verdict of guilty on all counts, Bianchini filed a motion for a new trial on the ground that the events involving Tenner denied him the right to trial by an impartial jury. In an opinion and order dated March 18, 1991, Judge Billings denied the motion. On September 19, 1991, Bianchini was sentenced to a term of 250 months imprisonment on the drug charges and to a term of 60 months on the Travel Act count running concurrently, to be followed by five years of supervised release. In addition, he was fined a total of $25,0.00 and was assessed $50 on each of the five counts. This appeal followed.
Bianchini maintains that the decision to allow Tenner to continue to sit on the jury for two days while the F.B.I. investigated the bribery attempt deprived him of a fair trial, and that the failure to grant a new trial after the jury returned the guilty verdicts constituted reversible error. We disagree. “The Constitution ‘does not require a new trial every time a *48juror has been placed in a potentially compromising situation.’ ” United States v. Aiello, 771 F.2d 621, 629 (2d Cir.1985) (quoting Rushen v. Spain, 464 U.S. 114, 104 S.Ct. 453, 78 L.Ed.2d 267 (1983) (per curiam)). As the Supreme Court has stated:
[I]t is virtually impossible to shield jurors from every contact or influence that might theoretically affect their vote. Due process means a jury capable and willing to decide the case solely on the evidence before it, and a trial judge ever watchful to prevent prejudicial occurrences and to determine the effect of such occurrences when they happen.
Smith v. Phillips, 455 U.S. 209, 217, 102 S.Ct. 940, 946, 71 L.Ed.2d 78 (1982).
At trial Bianchini never objected to Judge Billings’ handling of the jury. He cannot now raise the issue for appellate review. Although the judge did not inform counsel of every development as it unfolded, Bianchini was alerted to the attempted bribery well before the close of defendant’s case. He did not demand a mistrial, however, until after the verdicts were returned. When faced with similar situations in the past, “we have [had] no hesitation in rejecting, on waiver grounds, [such] tardily raised claim[s].” United States v. Bufalino, 576 F.2d 446, 451 (2d Cir.), cert, denied, 439 U.S. 928, 99 S.Ct. 314, 58 L.Ed.2d 321 (1978).
The district court has wide discretion to address the effects of unauthorized third party contact on a jury. See, e.g., Marshall v. United States, 360 U.S. 310, 312, 79 S.Ct. 1171, 1172, 3 L.Ed.2d 1250 (1959); United States v. Chang An-Lo, 851 F.2d 547, 558 (2d Cir.), cert, denied, 488 U.S. 966, 109 S.Ct. 493,102 L.Ed.2d 530 (1988); Aiello, 771 F.2d at 629; United States v. Weiss, 752 F.2d 777, 783 (2d Cir.), cert, denied, 474 U.S. 944, 106 S.Ct. 308, 88 L.Ed.2d 285 (1985). “[W]hether the impact of such contact denied an accused his fundamental right to a fair trial turns on the ‘special facts’ of each case,” facts best left to the judgment of the district court. Sher v. Stoughton, 666 F.2d 791, 795 (2d Cir. 1981). Where as here the defendant is also a prime suspect in the government’s jury tampering investigation, the trial judge must have the discretion necessary to balance the interest in discovering the truth against the interest of a fair trial. Cf. United States v. Moten, 582 F.2d 654, 660-62 (2d Cir.1978).
When first alerted to the bribery attempt, Judge Billings questioned Tenner in chambers, outside the presence of counsel. We have repeatedly sanctioned this approach. See Bufalino, 576 F.2d at 451; United States v. Miller, 381 F.2d 529, 540 (2d Cir.1967), cert, denied, 392 U.S. 929, 88 S.Ct. 2273, 20 L.Ed.2d 1387 (1968). When Tenner reported that he could not remain impartial, Judge Billings replaced him with an alternate juror before the jury began its deliberations. Cf. Remmer v. United States, 347 U.S. 227, 74 S.Ct. 450, 98 L.Ed. 654 (1954) (allowing tainted juror to participate in verdict creates presumption of prejudice). Following Tenner’s dismissal, the judge informed counsel about what had occurred. See Aiello, 771 F.2d at 629-30 (advising counsel after voir dire of juror held harmless as long as no prejudice resulted).
In the presence of counsel, Judge Billings then conducted voir dire of the other jurors to determine whether any of them had been exposed to impermissible contact. When two jurors reported that Tenner had spoken with them about the insanity defense, Judge Billings continued voir dire in chambers to determine whether they could remain impartial. See Chang An-Lo, 851 F.2d at 558-59 (recommending this approach).
There is no reason to believe that Tenner’s dismissal before the jury began to deliberate prejudiced the verdict or that the third-party conduct affected the other jurors. Judge Billings’ conduct of the proceedings ensured Bianchini’s right to an impartial jury. Cf. United States v. Ruggiero, 928 F.2d 1289, 1300 (2d Cir.) (no violation of right to impartial jury when juror’s dismissal came after jury had already begun deliberations and after he had spoken with other jurors about third-party *49contact), cert, denied, — U.S. -, 112 S.Ct. 372, 116 L.Ed.2d 324 (1991).
Next, Bianchini argues that Judge Billings erred in refusing to give a jury-instruction on the consequences of a verdict of not guilty by reason of insanity. Bianchini claims that the Insanity Reform Act of 1984, 18 U.S.C. §§ 4241-4247, requires such an instruction.
Federal courts usually instruct juries not to consider a verdict's consequences. See Rogers v. United States, 422 U.S. 35, 40, 95 S.Ct. 2091, 2095, 45 L.Ed.2d 1 (1975) (“the jury [has] no sentencing function and should reach its verdict without regard to what sentence might be imposed”). Judge Billings gave a typical instruction:
[T]he punishment provided by law for the offenses charged in the indictment or any resulting proceeding ... [including the] result of the plea of not guilty by reason of insanity is a matter exclusively [within] the province of the judge and should never be considered by the jury in arriving at an impartial verdict as to the guilt or innocence of the accused.
The Insanity Reform Act on its face does not compel more, and courts interpreting the Act have usually refused to adopt Bianchini’s position. See, e.g., United States v. Frank, 956 F.2d 872, 878-82 (9th Cir.1991). But cf. United States v. Neavill, 868 F.2d 1000, vacated, reh’g en banc granted, 877 F.2d 1394, appeal dismissed en banc, 886 F.2d 220 (8th Cir.1989).
The only textual support Bianchini cites for his argument comes from a Senate Committee report that reads:
[T]he jury, in a case in which the insanity defense has been raised, may be instructed on the effect of a verdict of not guilty by reason of insanity. If a defendant requests that an instruction not be given, it is within the discretion of the court whether to give it or not.
S.Rep. No. 98-225, 98th Cong., 1st Sess. 240, reprinted in 1984 U.S.C.C.A.N. 3182, 3422 (emphasis added). We read this language to leave the instructional decision to the discretion of the district court. We find no abuse of discretion.
Finally, Bianchini objects to Judge Billings’ method of calculating the amount of marijuana involved for sentencing purposes. To arrive at a figure for sentencing, the judge began with the number of marijuana plants seized during the police searches, estimated the number of plants grown previously, and applied the sentencing guidelines to treat each plant as the equivalent, of one kilogram of marijuana. U.S.S.G. § 2D1.1 (ratio for offenses involving 50 or more plants). Bianchini does not contest the application of the ratio for the growing plants seized during the search, but he contends that the estimates of past growing activity should been based on evidence of weight produced, not plants grown.
Other courts interpreting the ratios have concluded that the intent of the guidelines was “to measure live marijuana by the number of plants and dry leaf marijuana by weight.” United States v. DeLeon, 955 F.2d 1346, 1350 (9th Cir.1992); see also United States v. Osburn, 955 F.2d 1500, 1509 (11th Cir.1992) (recognizing “anomaly” in applying ratio before harvesting and actual weight after harvesting); United States v. Corley, 909 F.2d 359, 361 (9th Cir.1990) (live plants measured by number, dried marijuana by weight). We believe this approach best comports with congressional intent in passing its mandatory sentencing provision, 21 U.S.C. § 841(b)(l)(B)(vii), and with the rationale for the corresponding sentencing guideline, U.S.S.G. § 2D1.1.
Uncontroverted evidence indicates that Bianchini’s farms produced an amount of marijuana substantially less than that used for sentencing. Vermont State Police Detective Sergeant George Contois, Jr., testified on direct examination at trial and on cross examination during an evidentiary hearing that each of the two farms produced 7 to 10 pounds (3.2 to 4.5 kilograms) of marijuana bud per month and that the amounts harvested were certainly less than one kilogram per plant. State witness and co-conspirator Allan Blume testified that one farm produced 6 to 10 pounds (2.7 to 4.5 kilograms) of marijuana per month. *50The total dry weight of marijuana produced over the life of the operations, when added to the 3,700 plants actually seized, might support a sentence for 4,000 kilograms. This amount differs materially from the 11,100 kilograms used for sentencing. Because the evidence does not support the finding upon which the district court imposed sentence, we remand for resentenc-ing.
Conviction affirmed and case remanded for resentencing.
. One co-conspirator, Allan Blume, pled guilty and cooperated with the government. Another co-conspirator, Brian Brophil, is a fugitive.
. The investigation did not uncover the identity of the caller. There is no evidence to link Bianchini to the bribery attempt.