SPRECHER, Circuit Judge.
Following a jury trial, defendant was found guilty of wilfully and by means of threats endeavoring to influence, intimidate and impede a witness in the discharge of her duty in a pending criminal case in violation of 18 U.S.C. § 1503. He was subsequently sentenced to the maximum term of five years imprisonment. On appeal, defendant challenges both his conviction and his sentence.
I
Defendant first contends that he was not subject to prosecution under 18 U.S.C. § 15031 because the conduct alleged in the indictment occurred in the presence of the court and, therefore, was punishable, if at all, only as contempt of court under 18 U.S.C. § 401(1).2 We disagree.
The government is generally entitled to proceed under either of two applicable criminal statutes. United States v. Ruggiero, 472 F.2d 599, 606 (2d Cir.), cert. denied, 412 U.S. 939, 93 S.Ct. 2772, 37 L.Ed.2d 398 (1973); United States v. Zouras, 497 F.2d 1115, 1121 n. 16 (7th Cir. 1974). And this rule has been applied in the present context. As the Supreme Court noted in Savin, Petitioner, 131 U.S. 267, 275, 9 S.Ct. 699, 701, 33 L.Ed. 150 (1889):
It is contended that the substance of the charge against the appellant . is embraced by § 5399 [the predecessor of § 1503], and, it is argued, is punishable only by indictment. Undoubtedly the of-fence charged is embraced by that section, and is punishable by indictment. But the statute does not make that mode exclusive, if the offence is committed under such circumstances as to bring it within the power of the court under § 725 [the predecessor of § 401(1)] .
Thus, there is ample authority to support the conclusion that misbehavior falling within the literal ambit of both sections is punishable under either. See also Nye v. United States, 313 U.S. 33, 49, 61 S.Ct. 810, 85 L.Ed. 1172 (1941); Pettibone v. United States, 148 U.S. 197, 206, 13 S.Ct. 542, 37 L.Ed. 419 (1893); Sharon v. Hill, 24 F. 726 (C.C.Cal.1885); United States v. Walasek, 527 F.2d 676, 680 (3d Cir. 1975).
In support of his claim that the coverage of the two provisions cannot overlap, defendant cites United States v. Essex, 407 F.2d 214 (6th Cir. 1969). Essex correctly states that section 401(1) was originally enacted to restrict the summary contempt power of the federal courts. This was accomplished by limiting the covered conduct to that which occurs within the physical vicinity of the court. Nye, supra, 313 U.S. at 48-49, 61 S.Ct. 810. Congress contemplated that misbehavior not subject to the summary contempt power could still be reached by indictment under another criminal statute such as Section 1503. Id. at 52, 61 S.Ct. 810. However, there is nothing in the legislative history discussed in Essex which indicates a congressional intent to prohibit proceeding by indictment where exercise of the summary contempt power would be permissible. Indeed, such a prohibition would be inconsistent with the purpose of Section 401(1), i. e., to restrict, not expand, the exercise of the summary contempt jurisdiction. As the Third Circuit recently stated:
In view of the historical background set forth in Essex, the possibility that the conduct which . . . [defendant] was [369]*369found to have engaged in might be covered by § 401 . . . does not suggest that the conduct should not be found to be within § 1503. Of course, there are many instances in which a single course of conduct may violate more than one statute.
Walasek, supra, 527 F.2d at 680 (emphasis in original).
II
Defendant next contends that the evidence adduced at trial was insufficient to support his conviction under Section 1503. The word “endeavor” in Section 15033 “describes any effort or essay to do or accomplish the evil purpose that the section was enacted to prevent.” United States v. Russell, 255 U.S. 138, 143, 41 S.Ct. 260, 261, 65 L.Ed. 553 (1921). The endeavor need not be successful, but it must have at least a reasonable tendency to impede the witness in the discharge of her duties. United States v. DeStefano, 476 F.2d 324, 330 (7th Cir. 1973); United States v. Jackson, 168 U.S. App.D.C. 198, 513 F.2d 456, 460 (1975); United States v. Roe, 529 F.2d 629, 632 (4th Cir. 1975). Also, while it is necessary to establish that the charged conduct was intended to impede the witness, “[ijntent may, and generally must, be proved circumstantially; normally, the natural probable consequences of an act may satisfactorily evidence the state of mind accompanying it, even when a particular mental attitude is a crucial element of the offense. We perceive nothing that would divert cases of the instant type from this branch of legal doctrine.” Jackson, supra, 513 F.2d at 461 (footnotes omitted).
With these principles in mind, the case against defendant may be briefly summarized. On June 21, 1974, Jevita Hobbs was testifying as a witness for the government in United States v. Garland Jeffers, et al., 520 F.2d 1256 (7th Cir.) involving an alleged conspiracy to distribute heroin. On the same date, defendant, accompanied by his sister, attended the Jeffers trial. Ms. Hobbs had at one time been married to one of the Jeffers defendants and she possessed personal knowledge of the other defendants and their activities. She also knew defendant’s sister to be the girlfriend of Garland Jeffers, and she had met defendant on several occasions at the apartment where defendant’s sister and Jeffers were living. Ms. Hobbs had also known defendant to associate with Nathaniel Jeffers, who was also a defendant in the Jeffers case.4
Ms. Hobbs testified in the case at bar that, after referring to defendant several times during her Jeffers testimony and while answering a question later during the same testimony, she observed defendant “standing up and shaking his fist” and heard him say “you better not.” Ms. Hobbs interpreted defendant’s actions and words as a threat calculated to impede her continued testimony. She further testified that a recess was called at this point and she was taken from the courtroom to pull herself together because, in her words, “I wasn’t going to finish testifying.” After being [370]*370assured of her safety while in the courtroom, she returned to the stand and completed her testimony.
A Special Agent with the Drug Enforcement Administration then testified that defendant, while standing facing the witness stand, shook his fist and head in a negative direction. The agent further testified that defendant appeared to be speaking, but the agent did not hear what was said. A Deputy United States Marshall then testified along similar lines and added that defendant’s actions continued for approximately thirty seconds.
The final witness for the government was the judge who presided at the Jeffers trial. He stated:
I noticed that the testimony of Miss Hobbs was coming out very slowly. Her answers were, there were long pauses between the questions and the answers, I noticed that she was looking in the back of the courtroom and at approximately that same time I saw Mr. Harris stand up in the back of the courtroom and for an instant I observed him shake his fist and move his lips facing in the direction of the witness stand.
The judge also testified that Ms. Hobbs was “fairly well shaken” by the incident.
While the evidence is not overwhelming, when viewed in the light most favorable to the government, we are satisfied that it is sufficient for the jury to have inferred defendant’s guilt beyond a reasonable doubt of endeavoring to impede Ms. Hobbs’ testimony in the Jeffers case. Glasser v. United States, 315 U.S. 60, 80, 62 S.Ct. 457, 86 L.Ed. 680 (1942).
Ill
Defendant also claims that he was deprived of effective assistance of counsel in violation of the Sixth Amendment. In United States ex rel. Williams v. Twomey, 510 F.2d 634 (7th Cir. 1975), this court articulated the standards governing whether a defendant has been afforded constitutionally adequate assistance of counsel:
[This determination] goes.beyond an inquiry as to whether the . ■ . trial was a sham or mockery. But . [it does not go] to the point ... of declaring that there is at least a presumption of failure to meet the constitutional guarantee of assistance of counsel merely because defendant’s attorney makes egregious errors, tactical or strategic, in preparation, in conference, in examining witnesses, or in not investigating or calling potential witnesses. The criminal defendant . . . has the constitutional right to an advocate whose performance meets a minimum professional standard.
Id. at 640.
We are convinced that defendant has failed to meet his burden of showing the representation he received fell short of the Twomey standard. Matthews v. United States, 518 F.2d 1245, 1246 (7th Cir. 1975). To support his claim, defendant places considerable reliance upon trial counsel’s alleged failure to call available occurrence witnesses on defendant’s behalf. However, there is no support in the record for defendant’s speculative belief that there existed courtroom observers, other than those in fact called by defense counsel, who, if called, would have testified to facts beneficial to defendant’s case. Nor is there any basis for defendant’s assertion that trial counsel failed to even investigate the possible existence of such witnesses. And defendant’s claim that trial counsel failed to utilize available material which was critical to effective impeachment of Ms. Hobbs’ testimony in the case at bar is also without foundation in the record.
The final ground urged in support of defendant’s incompetency of counsel claim relates to trial counsel’s cross-examination of the judge who presided at the Jeffers case. In response to questions concerning defendant’s emotional appearance during the courtroom incident, the judge replied that “there was a certain intensity about his appearance” and that “[i]t left the impression with me that he knew exactly what he was doing.” Defendant argues that the questions eliciting these responses [371]*371evidence defense counsel’s inadequacy. Defendant, however, overlooks the fact that this line of questioning was successfully employed with the previous witness, who testified that defendant had only “a general expression on his face” during the incident. The Sixth Amendment does not require perfect representation and we will not substitute our judgment “for counsel’s practical decisions in the hustings,” United States v. Robinson, 502 F.2d 894, 896 (7th Cir. 1974), simply because hindsight might suggest that it was a mistake to repeat a previously successful cross-examination tactic.5
IV
Defendant was sentenced to imprisonment for a period of five years, which is the maximum term authorized by Section 1503. He contends that even if his conviction is allowed to stand his sentence should be vacated and the case remanded for resen-tencing.6 He argues that, in light of the absence of aggravating circumstances and the favorable background evaluation made by the probation officer who handled the investigation and prepared the presentence report,7 the sentence imposed was excessive and the trial judge must have relied upon the erroneous and extremely prejudicial hearsay-on-hearsay allegations added to the presentence report by a probation officer who was not involved in the presentence investigation.8
[372]*372The Supreme Court has consistently adopted the position that the courts of appeals have no authority to review the duration or severity of a sentence which is within the range set by statute. In Townsend v. Burke, 334 U.S. 736, 68 S.Ct. 1252, 92 L.Ed. 1690 (1948), the Court stated:
We would make clear that we are not . [vacating the sentence] because of petitioner’s allegation that his sentence was unduly severe. The sentence being within the limits set by the statute, its severity would not be grounds for relief here even on direct review of the conviction .
Id. at 741, 68 S.Ct. at 1255. The Court recently restated this position in Dorszynski v. United States, 418 U.S. 424, 94 S.Ct. 3042, 41 L.Ed.2d 855 (1974):
“If there is one rule in the federal criminal practice which is firmly established, it is that the appellate court has no control over a sentence which is within the limits allowed by a statute.”
Id. at 440-41, 94 S.Ct. at 3051 (citation omitted).9 Hence, even though we think the evidence supporting defendant’s conviction, while legally sufficient, was less than overwhelming and despite our belief that defendant’s courtroom behavior, while deplorable, was not such as to warrant imposition of the maximum sentence, we are unable to vacate defendant’s sentence simply because we deem it excessive.
This conclusion, however, does not dispose of defendant’s claim. As the Court in Dorszynski stated:
“Appellate modification of a statutorily-authorized sentence . . . is an entirely different matter than the careful scrutiny of the judicial process by which the particular punishment was determined. Rather than an unjustified incursion into the province of the sentencing judge, this latter responsibility is, on the contrary, a necessary incident of what has always been appropriate appellate review of criminal cases.”
418 U.S. at 443, 94 S.Ct. at 3053 (emphasis in original; citation omitted). Hence, the process by which the trial judge determined the sentence in the case at bar is not insulated from appellate review. See United States v. Hartford, 489 F.2d 652 (5th Cir. 1974); United States v. Daniels, 446 F.2d 967 (6th Cir. 1971).
In determining an appropriate punishment, all the circumstances of the particular crime and the background of the individual offender must be considered.10 This individualized sentencing process requires “possession of the fullest information possible concerning the defendant’s life and characteristics," Williams v. New York, 337 U.S. 241, 247, 69 S.Ct. 1079, 1083, 93 L.Ed. 1337 (1949), and that information is not limited to what is admissible at trial. United States v. Tucker, 404 U.S. 443, 446, 92 S.Ct. 589, 30 L.Ed.2d 592 (1972); Williams v. New York, supra, 337 U.S. at 247, 69 S.Ct. 1079.11 Accordingly, it is now beyond dispute that reliance upon hearsay in assessing punishment is not per se improper:
[373]*373[OJnce the guilt of the accused has been properly established, the sentencing judge, in determining the kind and extent of punishment to be imposed, is not restricted to evidence derived from the examination and cross-examination of witnesses in open court but may, consistently with the Due Process Clause of the Fourteenth Amendment, consider responsible unsworn or “out-of-court” information relative to the circumstances of the crime and to the convicted person’s life and characteristics.
Williams v. Oklahoma, 358 U.S. 576, 584, 79 S.Ct. 421, 426, 3 L.Ed.2d 516 (1959); Williams v. New York, supra.12 However, the Supreme Court has never suggested that consideration of hearsay is always proper. In Williams v. New York, the narrow issue was whether reliance on hearsay in determining an appropriate sentence was ever permissible and the Court specifically noted that the accuracy of the hearsay information relied on by the sentencing judge in that case “were not challenged by appellant or his counsel, nor was the judge asked to disregard any of them or to afford appellant a chance to refute or discredit any of them by cross-examination or otherwise.” 337 U.S. at 244, 69 S.Ct. at 1081.13 It is necessary, therefore, to determine what, if any, safeguards exist on the consideration of hearsay information in the sentencing process.14
In Townsend v. Burke, supra, the Supreme Court held that it violated due process to sentence a defendant “on the basis of assumptions concerning his criminal record which were materially untrue.” 337 U.S. at 741, 68 S.Ct. at 1255. The Court noted that the defendant, being unrepresented by counsel, had no opportunity to correct the false foundation upon which his sentence was premised. Id. Similarly, in United States v. Tucker, supra, the Court set aside a sentence because it was based, at least in part, upon prior convictions which were subsequently held constitutionally invalid because obtained while defendant was not represented by counsel. Tucker and Townsend have been read broadly to preclude reliance upon “improper or inaccurate information” in making the sentencing determination. Dorszynski, supra, 418 U.S. at 431 n. 7, 443, 94 S.Ct. 3042; McGee v. United States, 462 F.2d 243, 245 n. 2 (2d Cir. 1972); United States v. Espinoza, 481 F.2d 553, 555 (5th Cir. 1973).15
The Townsend-Tucker principle, however, is to some extent inconsistent with the principle of Williams v. New York and its progeny. The former reflects the Court’s belief that a defendant should not be sentenced on invalid premises. The latter, i. e., that consideration of hearsay information regarding defendant’s life and characteristics is generally permissible, reflects the Court’s concern that the trial judge exercise his individualized sentencing discretion in an informed manner. While both principles are premised on a concern that the sentencing process be objective and fair to the individ[374]*374ual defendant,16 the policies underlying Williams cannot be inflexibly advanced without undermining the policies underlying Townsend and Tucker, since hearsay allegations, by their very nature, are prone to error or inaccuracy. Hence the courts of appeals have found it necessary to strike a balance between the two principles in order to give adequate recognition to both.
In striking this balance, the courts have held that a defendant is entitled to some protection against the danger of reliance on erroneous hearsay allegations in the assessment of punishment. Specifically, it has been held that where the sentencing judge relies upon prejudicial hearsay information, the accuracy of which is contested,17 “fundamental fairness requires that a defendant be given at least some opportunity to rebut that information.” United States v. Espinoza, supra, 481 F.2d at 556. In applying this principle to the case at bar, we are confronted with several problems.
First, the cases frequently state that this rule only applies where the sentencing judge has explicitly relied on prejudicial hearsay information regarding the offender’s background. See, e. g., United States v. Walker, 469 F.2d 1377, 1380 (1st Cir. 1972); United States v. Espinoza, supra, 481 F.2d at 556. And the court below did not state the factors it considered in imposing the maximum sentence upon defendant. However, several considerations persuade us that the lack of explicit reliance in this case is not dispositive of defendant’s claim.
The vindication of a defendant’s right to not be sentenced on the basis of improper factors or erroneous information — a right recognized by the Court in Townsend and Tucker — should not depend upon the fortuity of the sentencing judge disclosing, perhaps inadvertently, the factors relied upon in the imposition of sentence. The fairness of the sentencing process is undermined by reliance upon inaccurate information, not by the sentencing judge stating that he relied upon material which proves to be inaccurate. In addition, the explicit reliance requirement simply encourages judges not to disclose the factors considered in imposing sentence. While it is true that a trial judge is generally not obligated to give reasons for the imposition of a particular sentence, it is sometimes necessary, and always advisable, to do so. See, e. g., McGee v. United States, 462 F.2d 243, 247 (2d Cir. 1972); United States v. Carden, 428 F.2d 1116, 1118 (8th Cir. 1970). Accordingly, we should not adopt a rule which will have the natural and probable effects of encouraging trial judges to avoid [375]*375giving reasons for sentencing decisions and diminishing the individual offender’s confidence in the fairness and objectivity of-a critical step in the criminal justice process.
Moreover, a showing of explicit reliance on improper factors of erroneous information has not invariably been held a prerequisite to sentence relied under Townsend and Tucker. For example in McGee, supra, it was not possible to determine whether the sentence imposed was affected by consideration of unlawful convictions.18 The Second Circuit, in an opinion by Judge Friendly, concluded that it was not necessary to show explicit reliance to obtain relief. It was sufficient to show that it was not improbable the trial judge was influenced by improper factors in imposing sentence. We think this test is met here. The evidence supporting the conviction was not overwhelming. The conduct for which defendant was convicted was not accompanied by aggravating circumstances.19 And, most important, there was a distinct disparity in the presentence report between the evaluative summary of defendant’s life and background prepared by the probation officer who handled the presentence investigation20 and the hearsay-on-hearsay allegations added to the report by an officer who was not involved in the background investigation.21 Under these circumstances, it is not unreasonable to conclude that the court below, in imposing the maximum sentence, may have been influenced by the hearsay allegations in the presentence report.. Accordingly, defendant’s claim is not defeated simply because the sentencing judge elected not to articulate the factors considered in imposing sentence.
A second obstacle to reconsideration of defendant’s sentence is the fact that the hearsay material in the presentence report was not challenged as inaccurate until this appeal. It is settled that relief is unavailable where the accuracy of the information considered by the sentencing judge is conceded. Williams v. New York, supra; Williams v. Oklahoma, supra. There is no contention here that the sentencing judge refused to disclose that portion of the presentence report containing the challenged hearsay statements, and yet neither defendant nor his trial counsel challenged the accuracy of the prejudicial allegations during the sentencing hearing. As a general rule, we would agree that sentence relief should be foreclosed where a defendant, who is not denied access to the presentence report, “has not directly and specifically denied the truth of hearsay information” and the only denial of record is that of counsel on appeal. See United States v. Trevino, 490 F.2d 95, 96 (5th Cir. 1973).
Nevertheless, several considerations persuade us that, under the circumstances of this case, justice would not be disserved if defendant is simply afforded the opportunity to deny and rebut the allegations of serious criminal misconduct in the presentence report.
[376]*376First, defendant contends that his trial counsel apparently neglected to examine the presentence report prior to the sentencing hearing. While this contention has no factual support in the record, it is logically compelling. It seems incredible to us that, if defendant or his counsel had in fact seen the extremely prejudicial hearsay remarks prior to the sentencing hearing, there would have been no effort to challenge their accuracy.22
Second, there is a marked disparity in the presentence report between the background evaluation prepared by the investigating probation officer and the hearsay allegations appended to the report by a non-investigating officer. On the one hand, the investigating officer found that defendant held down two jobs with the same company and that the Chairman of the Board and Comptroller of the company considered defendant a very good employee. On the other hand, the appended hearsay information alleges that defendant was heavily involved in illicit drug trafficking.
Finally, the hearsay-on-hearsay statements, which charge defendant with criminal misconduct far more serious than that for which he was convicted, possess not indicia of reliability. The only basis for the charges is a statement by a Federal agent that he was told by unnamed members of the so-called Family that defendant was involved in that group’s drug operations.
In a situation similar to this the Ninth Circuit stated:
Here the other criminal conduct charged was very serious, and the factual basis for believing the charge was almost nil. It rested upon only two things: the opinion of unidentified personnel in the Bureau of Narcotics and Dangerous Drugs, and the unsworn statement of one agent that an informer had given him some information lending partial support to the charge.
[A] sentence cannot be predicated on information of so little value as that here involved. A rational penal system must have some concern for the probable accuracy of the informational inputs in the sentencing process.
On resentencing, the District Court may not rely upon the information contained in the presentence report unless it is amplified by information such as to be persuasive of the validity of the charge there made.
United States v. Weston, 448 F.2d 626, 633, 634 (1971). In Weston, however, the accuracy of the hearsay accusations was fully contested prior to imposition of sentence. The court, therefore, had to determine whether it had the authority to decide that some hearsay material was so unreliable it could not be considered in imposing sentence even if defendant was afforded an opportunity to rebut the allegations. In contrast, the sentencing judge in the case at bar had no reason to question the truth of the hearsay accusations, or to require the government to submit additional material in support of them, since neither defendant nor his counsel contested their accuracy pri- or to sentencing. The court below could hardly be faulted if in fact it considered the hearsay allegations contained in the presen-tence report. For, even though they seem devoid of informational value, it must have appeared to the court that defendant was conceding their accuracy. See Williams v. New York, supra.
However, if defendant had contested their accuracy prior to sentencing and the government failed to supply any additional material to corroborate them, the court might have concluded that the charges of other criminal misconduct in the presen-tence report were too unreliable to be considered in the imposition of sentence.
[377]*377Here, unlike in Weston, the sentencing judge has never had an opportunity to make this assessment. Therefore, we vacate the sentence and remand to the district court for resentencing after affording defendant adequate opportunity to contest the accuracy of the serious charges contained in the presentence report. While the sentencing judge is free to reimpose the original sentence upon reconsideration, we are confident that he will give careful consideration to defendant’s claim for sentence relief.23
Accordingly, the judgment of conviction is affirmed, but the sentence vacated and the case remanded for further proceedings consistent with this opinion.
AFFIRMED IN PART; REMANDED IN PART.