Billy Sunday Birt, a state prisoner, appeals the denial of his federal habeas corpus petition challenging state convictions for murder, armed robbery, and burglary. Birt contends that he was denied the right to counsel of his choice as guaranteed by the sixth and fourteenth amendments. Because the factfinding procedure employed by the state habeas corpus court did not afford a full and fair hearing on this contention, we vacate the denial of Birt’s petition and remand to the district court for further proceedings consistent with this opinion.
I. Procedural History 1
On January 31, 1975, a Jefferson County, Georgia, grand jury returned an indictment charging Birt and three others with one count of burglary, two counts of armed robbery, and two counts of murder in connection with the deaths of Reid and Lois Fleming, husband and wife. At the time of indictment, Birt was incarcerated in Illinois on an unrelated federal conviction and did not learn of the indictment until March or April of 1975. He was not transferred to Georgia until shortly before arraignment on June 7, 1975. After a six-day trial in the Jefferson County Superior Court beginning on June 23,1975, a jury found Birt guilty of all charges and recommended that he be sentenced to death. On June 28, 1975, the trial court imposed two sentences of death for the murder counts, two concurrent life sentences for the armed robbery counts, and twenty years imprisonment for the burglary count. On direct appeal, the Supreme Court of Georgia affirmed the convictions and sentences. Birt v. State, 236 Ga. 815, *693225 S.E.2d 248, cert. denied, 429 U.S. 1029, 97 S.Ct. 654, 50 L.Ed.2d 632 (1976).
Birt filed a petition for writ of habeas corpus in the Superior Court of Tattnall County, Georgia. After an evidentiary hearing, that court determined that the constitutional inadequacies of the sentencing phase jury instructions required vacating Birt’s death sentences and that a new sentencing hearing be held.2 All other asserted grounds for relief involving alleged defects in the guilt-innocence phase of Birt’s trial were denied. The Georgia Supreme Court upheld the decision of the state habeas corpus court. Birt v. Hopper, 245 Ga. 221, 265 S.E.2d 276, cert. denied, 449 U.S. 855, 101 S.Ct. 150, 66 L.Ed.2d 68 (1980).
Birt next sought collateral relief in the United States District Court for the Southern District of Georgia and requested an evidentiary hearing. Finding that the state courts accorded Birt a full and fair hearing on all asserted grounds for relief and that none of the statutory exceptions in 28 U.S. C.A. § 2254(d)(l)-(8) applied, the district court presumed the state court’s factual findings to be correct. Thus, the district court held no evidentiary hearing. On February 16, 1982, the court entered an order denying habeas corpus relief. Birt v. Montgomery, 531 F.Supp. 815 (S.D.Ga.1982). Upon obtaining a certificate of probable cause, Birt timely filed this appeal.
II. Issues on Appeal
Birt raises five issues on appeal. He contends (1) that the factfinding procedures employed by the state habeas corpus court did not afford a full and fair hearing because Georgia law at the time did not recognize the validity of subpoenas issued beyond an 150-mile range of the courthouse, and therefore, crucial witnesses on Birt’s behalf, though subpoenaed, failed to attend; (2) that he was denied the right to counsel of his choice as guaranteed by the sixth and fourteenth amendments; (3) that he was denied the effective assistance of counsel because of his appointed lawyer’s failure to investigate the population figures of Jefferson County and the percentages of blacks and women on Jefferson County jury rolls; (4) that he was denied the right to a jury pool comprised of a representative cross-section of the community; and (5) that the security measures employed at trial deprived him of an impartial jury and due process in violation of the sixth and fourteenth amendments.
The standard of review for habeas corpus petitions filed by state prisoners is that stated in 28 U.S.C.A. § 2254(d).3 Written determinations concerning factual issues entered after a hearing on the merits by a state trial or appellate court of competent jurisdiction are presumed correct un*694less the petitioner can show that one of the conditions set forth in 28 U.S.C.A. § 2254(d)(l)-(8) exists. Hance v. Zant, 696 F.2d 940, 946 (11th Cir.1983). If such a showing is made, the presumption no longer applies and the petitioner has the burden of proving, by a preponderance of the evidence, the facts supporting his substantive federal claim. Thomas v. Zant, 697 F.2d 977, 985-987 (11th Cir.1983). If none of the conditions of section 2254(d)(l)-(8) are found to exist, the petitioner must be given an opportunity to rebut the presumption and establish by convincing evidence that the state court was erroneous. Sumner v. Mata, 449 U.S. 539, 546, 101 S.Ct. 764, 768, 66 L.Ed.2d 722 (1981); Hance, 696 F.2d 940, 946. The presumption of correctness accorded state court findings does not apply to legal findings or to mixed questions of fact and law. Cuyler v. Sullivan, 446 U.S. 335, 341-42, 100 S.Ct. 1708, 1714, 64 L.Ed.2d 333 (1980).
III. Discussion
A. The Right to Counsel of Choice and the Denial of a Federal Evidentiary Hearing
In his first substantive argument, Birt alleges that he was denied the right to counsel of his choice by the trial court’s refusal to allow him a meaningful opportunity to secure private counsel to prepare his defense. The facts pertaining to this claim, as found by the state habeas corpus court, are as follows. At the time of the indictment on January 31, 1975, Birt was incarcerated in the federal penitentiary in Marion, Illinois, on an unrelated federal conviction. Birt did not learn of the indictment until March or April when he received a telephone call from O.L. Collins, the attorney appointed by the Superior Court of Jefferson County to represent him. In this telephone conversation, Birt strenuously objected to appointed representation and told Collins to inform the Superior Court that upon transfer to Georgia, he would hire an attorney.4 Birt was not transferred to Georgia until shortly before arraignment on June 7, 1975. At arraignment, with Collins present, Birt continued his objection to appointed counsel and informed the court that, given the opportunity to speak with his wife, he would hire an attorney.5 Collins’s testimony at the state habeas corpus hearing confirms Birt’s objections to appointed counsel. The state habeas corpus *695court found that Birt objected to appointed counsel at arraignment, but that the trial court exercised its discretion in keeping Collins on the case in the event Birt was unable to retain counsel.
Although incarcerated in Augusta, Georgia, some 200 miles from his family in Marietta, Georgia, Birt and his family succeeded in retaining a private attorney, Eugene Reeves, to represent him at the upcoming trial. According to Collins, he, Reeves, and Birt met for the first time at the Richmond County jail on Sunday night, June 22, 1975, with trial scheduled to begin the next morning. Collins testified that when Reeves revealed his intention to seek a continuance in order to prepare for trial, he advised Reeves that Judge McMillan (who was also the arraigning judge), was unlikely to grant any continuances. Collins testified further that, after independent conversations with both attorneys, Birt decided to keep both of them.6 Birt’s testimony to the contrary was rejected by the state habeas corpus court.7 Birt proceeded to trial represented by both Collins and Reeves. The record indicates that Reeves cross-examined the state’s principal witness and handled most of the defense, examining Birt and his alibi witnesses.
The state habeas corpus court found that Birt voluntarily accepted the assistance of both Collins and Reeves and thereby waived the right to counsel of his choice. This finding was affirmed on appeal. Birt v. Hopper, 245 Ga. 221, 223, 265 S.E.2d 276, 278. As discussed above, this finding is entitled to the presumption of correctness unless one of the 28 U.S.C.A. § 2254(d) circumstances applies. Birt contends that section 2254(d)(2) is applicable because, according to Birt, the factfinding procedure employed by the state habeas corpus court was not adequate to afford a full and fair hearing on the right to counsel question. The basis of Birt’s argument is the Georgia statute in effect at the time of the habeas *696corpus hearing which restricted the enforceability of subpoenas to 150 miles from the courthouse where the habeas corpus proceeding is held. Ga.Code Ann. § 38-801(e) (revised and recodified at § 24-10-21 (1982)).8 This statute prevented Birt from compelling the attendance of Reeves, Birt’s retained attorney, at the state habeas corpus hearing. Although he subpoenaed Reeves, Birt could not compel Reeves attendance because his residence in Law-renceville, Georgia, is more than 150 miles from Tattnall County, Georgia. Consequently, Reeves was outside the range for an enforceable subpoena. Reeves allegedly would have testified to the Sunday night conversation between him, Collins, and Reeves, during which, according to the state habeas corpus court, Birt waived the right to counsel of his choice. The state urges us to decline consideration of Birt’s objection to the subpoena range statute because of his failure to challenge the statute on appeal from the denial of the state habeas corpus petition.9 Notwithstanding this failure, the state claims that the hearing Birt received in state court was full and fair. Because we agree with Birt that the procedural statute prevented a full and fair hearing on the right to counsel of choice question, we hold that it was error for the district court to presume the factual findings entered by the state habeas corpus court to be correct. It is therefore our view that Townsend v. Sain, 372 U.S. 293, 313, 83 S.Ct. 745, 757, 9 L.Ed.2d 770 (1963), mandates a federal evidentiary hearing on this issue.
In Townsend v. Sain, the Supreme Court delineated six situations where a federal evidentiary hearing is required even though a state court has previously entered factual findings. One of the situations envisioned by the Court is that presently codified in 28 U.S.C.A. § 2254(d)(2). See footnote 3. Townsend governs the threshold question of when a federal evidentiary hearing is mandatory while section 2254(d) establishes a presumption of correctness for state court findings unless one of its exceptions is established. Thomas v. Zant, at 984; Guice v. Fortenberry, 661 F.2d 496, 501 (5th Cir.1981) (en banc). Section 2254(d) also allocates the burdens of proof once a Townsend hearing is deemed necessary. Thomas, at 984. When one of the statutory exceptions applies, the state’s factual findings, while no longer entitled to a presumption of correctness, are not presumed incorrect, nor does the state have the burden of proving that the petitioner is not unconstitutionally confined. “Rather, any presumption of correctness simply drops out of the picture, and the traditional rules as to burden and standard of proof continue.” Developments in the Law — Federal Habeas Corpus, 83 Harv.L.Rev. 1038, 1142 (1970) (footnote omitted). Thus, at the Townsend hearing, Birt must establish by a preponderance of the evidence that he was denied the right to counsel of his choice. If he *697succeeds in establishing a prima facie case for an unconstitutional denial, the state may rebut the prima facie case by proving, with a preponderance of the evidence, that Birt voluntarily waived his right to counsel of his choice. See Thomas, at 985-87.
Our conclusion that the factfinding procedure employed by the state habeas corpus court was not adequate to afford a full and fair hearing on Birt’s sixth amendment claim stems from the fact that Reeves, the attorney retained by Birt and his family, could not be compelled to testify at the state hearing. The state brings to our attention the fact that under the Georgia habeas corpus statute, Birt could have obtained the testimony of Reeves by other methods, such as deposition or sworn affidavit. Ga.Code Ann. § 50-127(7) (recodi-fied at § 9-14 — 48 (1982)). The state habeas corpus court record reflects that Birt did in fact request an opportunity to introduce an affidavit from Reeves when it appeared that he was not going to honor the subpoena. The state habeas corpus court, however, concluded the hearing with a simple notation of Birt’s objection.10
Birt offers no suggestion as to what Reeves’s testimony would disclose. It can be inferred from the absence of any objections from Birt on the morning of trial, and the absence of a motion by Reeves for a continuance, that Birt did waive his right to counsel of his choice and voluntarily chose to proceed to trial with retained and appointed counsel. We choose not to base our holding on such an inference, however, especially when the state habeas corpus hearing resulted in a virtual swearing match. Caution is dictated because the swearing match was between, on the one hand, a convicted felon, and on the other, the attorney appointed to represent him, himself a former district attorney charged in Birt’s petition with rendering ineffective assistance. It is not difficult to predict the victor in such a match. In this regard, the sixth amendment, while not providing an absolute right, guarantees a defendant a fair opportunity to secure counsel of his choice. Powell v. Alabama, 287 U.S. 45, 53, 53 S.Ct. 55, 58, 77 L.Ed. 158 (1932). Whether Birt waived this guarantee deserves more inquiry than just Birt’s word against Collins’s. Because we find that statutory procedures then in force prevented a full and fair inquiry on this issue, Townsend directs that an evidentiary hearing be held in federal court. At that hearing, the respective burdens are as discussed above. If it is found that Birt’s right to counsel of his *698choice was denied, his convictions must be overturned and a new trial granted.
B. Traverse Jury Pool Challenge
Birt claims that the traverse jury list from which his trial jury was selected substantially underrepresented blacks and women by percentages violative of both the sixth amendment right to a jury pool representative of a fair cross-section of the community and the fourteenth amendment guarantee of equal protection. See Duren v. Missouri, 439 U.S. 357, 99 S.Ct. 664, 58 L.Ed.2d 579 (1979); Castaneda v. Partida, 430 U.S. 482, 97 S.Ct. 1272, 51 L.Ed.2d 498 (1977); Taylor v. Louisiana, 419 U.S. 522, 95 S.Ct. 692, 42 L.Ed.2d 690 (1975). On appeal from the denial of Birt’s state petition, the Georgia Supreme Court found that according to Georgia law in effect at the time of trial, the traverse jury challenge was waived for purposes of habeas corpus review due to the failure to assert the challenge prior to trial. The court thus refused to entertain the claim. Birt v. Hopper, 245 Ga. 221, 223, 265 S.E.2d 276, 278.11 The district court entered a similar finding, and, concluding that cause for the failure to object had not been established, refused to reach the merits. Birt v. Montgomery, 531 F.Supp. 815, 818 n. 2.
Under Georgia law at the time of Birt’s trial, “the right to object to the composition of the ... traverse jury will be deemed waived ... unless the person challenging the sentence shows in the petition and satisfies the court that cause exists for his being allowed to pursue the objection after the sentence and conviction have otherwise become final.” Ga.Code Ann. § 50-127(1) (recodified at § 9-14-42(b) (1982)). To assert a jury composition challenge collaterally in federal court when such right has been waived under state law, Francis v. Henderson, 425 U.S. 536, 96 S.Ct. 1708, 48 L.Ed.2d 149 (1976), requires the petitioner to demonstrate both cause for the failure to challenge and actual prejudice. Although arising in the context of a challenge to the composition of a grand jury, Francis v. Henderson has been applied to traverse jury attacks as well. See, eg., Huffman v. Wainwright, 651 F.2d 347 (5th Cir.1981); Evans v. Maggio, 557 F.2d 430, 434 n. 6 (5th Cir.1977); Cunningham v. Estelle, 536 F.2d 82, 83-84 (5th Cir.1976). “Absent cause for the procedural default and actual prejudice from the error, principles of comity and federalism prevent federal courts from granting habeas relief to state prisoners whose claim is non-reviewable in state court because of the default.” Washington v. Estelle, 648 F.2d 276, 278 (5th Cir.), cert. denied, 454 U.S. 899, 102 S.Ct. 402, 70 L.Ed.2d 216 (1981).
Birt’s federal petition lacks any discussion on the failure to challenge. In his brief on appeal, Birt argues that, because no evidentiary hearing was held in federal court, he lacked a full opportunity to demonstrate cause and prejudice. Even absent a full hearing, however, Birt claims the following combine to constitute sufficient cause: (i) the denial of the right to counsel of his choice, (ii) his appointed attorney’s misunderstanding of jury selection law, and (iii) Birt’s non-participation in appointed counsel’s decision not to challenge the traverse jury. We reject Birt’s contention that the failure to hold a federal evidentiary hearing precluded the opportunity to demonstrate cause and prejudice. Because Birt’s federal petition failed to allege any facts which, if proved, would have demonstrated cause and prejudice and therefore would have entitled Birt to relief, the district court was not required to hold an evidentiary hearing on this question. See Baldwin v. Blackburn, 653 F.2d 942, 947 (5th Cir.1981), cert. denied, 456 U.S. 950, 102 S.Ct. 2021, 72 L.Ed.2d 475 (1982); Rutledge v. Wainwright, 625 F.2d 1200, 1205 (5th Cir.1980), cert. denied, 450 U.S. 1033, 101 S.Ct. 1746, 68 L.Ed.2d 229 (1981). The alle*699gation concerning appointed counsel’s misunderstanding of jury selection law, interpreted properly, is a claim of ineffective assistance. Bare claims of ineffective assistance are insufficient to establish the requisite cause. Sullivan v. Wainwright, 695 F.2d 1306, 1311 (11th Cir.1983); Lumpkin v. Ricketts, 551 F.2d 680, 682 (5th Cir.), cert. denied, 434 U.S. 957, 98 S.Ct. 485, 54 L.Ed.2d 316 (1977). A finding of ineffective assistance, however, may satisfy the cause requirement. As discussed in the next section of this opinion, we make such a determination and find that Birt’s appointed counsel (Collins) rendered ineffective assistance due to his deficient investigation of Jefferson County population percentages and their relation to the county traverse jury list. Despite this determination of sufficient cause, Birt is not entitled to substantive relief on this issue because nothing in the record indicates that Birt satisfies the other requirement of Francis v. Henderson, that is, that he was actually prejudiced by the failure to challenge. Assuming that the Jefferson County traverse jury pool was composed unconstitutionally, Birt could benefit from such violation only if it worked to his actual and substantial disadvantage. See United States v. Frady, 456 U.S. 152, 170, 102 S.Ct. 1584, 1596, 71 L.Ed.2d 816, 832 (1982). If challenged prior to trial, a movant is not required to demonstrate prejudice flowing from an unconstitutionally composed jury pool. The prejudice is presumed. Cf. Rose v. Mitchell, 443 U.S. 545, 554, 99 S.Ct. 2993, 2999, 61 L.Ed.2d 739 (1979) (challenge to grand jury foreperson on equal protection grounds); Alexander v. Louisiana, 405 U.S. 625, 628, 92 S.Ct. 1221, 1224, 31 L.Ed.2d 536 (1972) (challenge to grand jury on equal protection grounds). On collateral attack in federal court, however, when the challenge has been waived under state law, the burden of demonstrating prejudice resulting from underrepresen-tation is much greater than the presumption accorded the violation when raised pri- or to trial. Cf. Frady, 456 U.S. 152, 164-66, 102 S.Ct. 1584, 1592-93, 71 L.Ed.2d 816, 828-29 (federal prisoner challenging jury instructions for first time in 28 U.S.C.A. § 2255 proceeding); Henderson v. Kibbe, 431 U.S. 145, 154, 97 S.Ct. 1730, 1736, 52 L.Ed.2d 203 (1977) (state prisoner challenging jury instructions initially in 28 U.S.C.A. § 2254 proceeding). Although difficult to define with precision, an actual and substantial disadvantage — that which must be demonstrated on collateral attack — means something more than disparity in population percentages on a traverse jury list. Because Birt failed to demonstrate anything more than disparity in the full and fair hearing held in the state habeas corpus court on this issue, no federal habeas corpus relief on this ground is warranted.
C. Assistance Rendered by Appointed Counsel
Birt challenges as ineffective only one aspect of appointed counsel’s representation. He contends that, although cognizant of the fact that prior Jefferson County traverse jury lists had underrepresented blacks and women and that the lists had been recently revised under challenge, appointed counsel nevertheless rendered ineffective assistance in failing to challenge the June 1975 list from which Birt’s jury was selected. Birt claims that appointed counsel knew neither the constitutional standards governing jury selection procedures nor the population percentages of blacks and women in the Jefferson County population. Thus, according to Birt, he lacked the mathematical means necessary to assess the representativeness of the traverse jury list and his decision to forego challenging that list was not an informed and tactical one.
Birt’s statistics show an absolute disparity of underrepresentation on the June 1975 list of 32.9% for blacks and 17.6% for women, figures which the state does not dispute.12 The statistics also indicate that tra*700verse jury pool lists for previous years comprised even fewer blacks and women and therefore involved higher race and gender disparities.13 Testimony of Jefferson County jury commissioners at the state habeas corpus hearing revealed that potential jurors were occasionally selected by accepting or rejecting names on the county voter registration lists based upon the commissioners personal knowledge of the individuals or their family background. The commissioners acknowledged that they did not obtain population figures for Jefferson County or calculate the proportionate representation of minorities in the general population.14
Birt’s statistical evidence appears to establish a prima facie case of unconstitutional composition under both the sixth and fourteenth amendments. The percentage disparities are sufficiently disproportionate to fall within the approximate boundaries delineated in other cases. See, e.g., Turner v. Fouche, 396 U.S. 346, 90 S.Ct. 532, 24 L.Ed.2d 532 (1970) (23%); Hernandez v. Texas, 347 U.S. 475, 74 S.Ct. 667, 98 L.Ed. 866 (1954) (14%); Preston v. Mandeville, 428 F.2d 1392 (5th Cir.1970) (13.3%). For purposes of the equal protection violation, the subjective judgments of the Jefferson County jury commissioners certainly renders the method of selection susceptible to possible abuse. See Castaneda v. Partida, 430 U.S. 482, 497, 97 S.Ct. 1272, 1281, 51 L.Ed.2d 498 (1977). For purposes of the sixth amendment right to a jury of a representative segment of the community, the disparities of blacks and women on Jefferson County traverse jury lists over a period of time indicates systematic exclusion of these two groups.
The state concedes that Collins was aware that an attack could be made on the composition of the traverse jury list. The state maintains, however, that Collins’s ha-beas corpus testimony, which was adopted by the state courts, is conclusive on the decision to forego a jury challenge. Collins testified that no challenge was made because, based upon his discussions with the jury commissioners, he was satisfied with the method of selection, and based upon his investigation and discussion with citizens of the county, he was satisfied with the composition of the jury list. According to the state, Collins’s investigation, accompanied by Birt’s insistence on proceeding to trial, makes the decision not to challenge one of trial strategy.
The district court characterized Collins’s decision not to challenge the traverse jury as a matter of trial strategy. The court noted that Collins filed a motion for change of venue with the stipulation that he would not insist upon such a change if the defense were able to draw a satisfactory jury. Collins testified that he was satisfied with the jury ultimately selected and he accordingly withdrew the change of venue motion.
The sixth amendment guarantees criminal defendants the right to counsel reasonably likely to render and rendering reasonably effective assistance given the totality of the circumstances. See, e.g., Washington v. Strickland, 693 F.2d 1243, 1250 (5th Cir. Unit B 1982) (en banc); MacKenna v. Ellis, 280 F.2d 592, 599 (5th Cir.1960), adhered to en banc, 289 F.2d 928 (5th Cir.), cert. denied, 368 U.S. 877, 82 S.Ct. 121, 7 L.Ed.2d 78 (1961). Whether counsel *701has rendered adequate assistance is a mixed question of fact and law requiring application of legal principles to the historical facts of the case. Cuyler v. Sullivan, 446 U.S. 335, 341-42, 100 S.Ct. 1708, 1714, 64 L.Ed.2d 333 (1980); Young v. Zant, 677 F.2d 792, 798 (11th Cir.1982). “The district court’s conclusion on this issue is entitled to no special deference and this court must review counsel’s performance and determine independently whether the constitutional standard was met.” Sullivan v. Wainwright, 695 F.2d 1306, 1308, citing Proffitt v. Wainwright, 685 F.2d 1227, 1247 (11th Cir.1982). Nor is the state court’s conclusion on this issue entitled to a presumption of correctness under 28 U.S.C.A. § 2254(d). Goodwin v. Balkcom, 684 F.2d 794, 804 (11th Cir.1982), cert. denied, - U.S. -, 103 S.Ct. 1798, 76 L.Ed.2d 364 (1983). Effective counsel need not be errorless counsel, nor should counsel’s performance be judged ineffective with the benefit of hindsight. Mylar v. State, 671 F.2d 1299, 1301 (11th Cir.1982), petition for cert. filed, 51 U.S.L.W. 3079 (U.S. Aug. 10, 1982) (No. 81-2240); Baty v. Balkcom, 661 F.2d 391, 394 (5th Cir.1981), cert. denied, 456 U.S. 1011, 102 S.Ct. 2307, 73 L.Ed.2d 1308 (1982). Essential to effective representation, however, is the independent duty to investigate and prepare. Goodwin, 684 F.2d 794, 805.
The charge of ineffective assistance directed at Collins implicates the extent of his investigation into a plausible line of defense. See Washington v. Strickland, 693 F.2d 1243, 1253. Before making a strategic choice as to which lines of defense to employ at trial, Washington v. Strickland teaches that “counsel should ideally perform a substantial investigation into each potential line.” 693 F.2d at 1253 (emphasis added).
When an attorney makes a strategic choice after satisfying this rigorous and extensive duty to investigate, courts will seldom if ever find that the choice was the result of ineffective assistance of counsel .... Whereas a strategy chosen after full investigation is entitled to almost automatic approval by the courts, a strategy chosen after partial investigation must be scrutinized more closely in order to safeguard the rights of criminal defendants.
Washington, 693 F.2d at 1254-55. In most cases, strategy employed without a reasonably substantial investigation into all plausible lines of defense will be in part based upon the attorney’s professional assumptions regarding the probable success of each line. The courts have found that a reasonable strategic choice based upon reasonable assumptions makes investigation into other plausible lines of defense unnecessary. See, e.g., Jones v. Kemp, 678 F.2d 929, 931-32 (11th Cir.1982); Gray v. Lucas, 677 F.2d 1086, 1093-94 (5th Cir.1982). Conversely, courts have found counsel ineffective where the failure to investigate is not based upon a reasonable set of assumptions or when those assumptions are not reasonable. See, e.g., Young v. Zant, 677 F.2d 792, 798-800; Kemp v. Leggett, 635 F.2d 453, 454-55 (5th Cir.1981).
Collins’s habeas corpus testimony convinces us that the decision not to challenge the traverse jury pool, while arguably the result of a reasonably substantial investigation, was not based upon an adequate understanding of the facts and applicable law. Collins testified that, although the revised jury list may not have accurately reflected a cross-section of the community, as far as he was concerned, it was fair. As the statistics indicate, however, in reality it was not. No matter how many times the jury commissioners were interviewed or jury lists examined, without knowledge of the racial and gender composition of Jefferson County, Collins was in no better position than one who had chosen not to investigate the jury pool at all. We cannot say •that Collins’s assumption that the revised jury list was fair was a reasonable one. Nor can we say that Collins’s choice not to challenge the traverse jury was a fully informed strategic decision. We therefore hold the district court’s finding to the contrary clearly erroneous. See Washington v. Strickland, 693 F.2d at 1257 n. 24; Beckham v. Wainwright, 639 F.2d 262, 265-66 (5th Cir.1981). Accordingly, we reject the dis*702trict court’s conclusion that Collins rendered effective assistance.15 A finding of ineffective assistance, however, does not end the inquiry. To prevail on this claim, “the petitioner must show that ineffectiveness of counsel resulted in actual and substantial disadvantage to the course of his defense.” Washington v. Strickland, 693 F.2d at 1262. To demonstrate the allegedly prejudicial consequences of Collins’s failure to challenge the traverse jury pool, Birt introduced the testimony of Dr. John H. Curtis, a university sociologist. Dr. Curtis opined that, based on his study of three South Georgia counties, blacks and women are more reluctant to convict and sentence to death than are whites and men generally.
Because both the state courts and the district court found Collins’s assistance to be reasonably effective, neither court reached the question of prejudice, an inquiry upon which Washington v. Strickland requires there be resolution. Because we are remanding to the district court for further proceedings on the question of Birt's right to counsel of his choice, we deem it appropriate to let the district court, in the first instance, address the issue of prejudice. As a preliminary matter, Birt must be given the opportunity to demonstrate that he suffered actual and substantial detriment because of Collins’s ineffective assistance. If Birt can demonstrate actual and substantial detriment, the district court must then give the state the opportunity to demonstrate that, in the context of the entire case, the detriment suffered was harmless beyond a reasonable doubt. See Washington v. Strickland, 693 F.2d at 1264.
D. Security Measures at Trial
Birt alleges that the security measures employed during trial turned the courtroom into an armed camp of law enforcement officials communicating apparent guilt and imminent dangerousness to the jury. He claims the security was unnecessarily excessive and deprived him of an impartial jury and due process in violation of the sixth and fourteenth amendments.
This claim has been addressed by the state courts in habeas corpus and by the district court. See Birt v. Hopper, 245 Ga. 221, 225, 265 S.E.2d 276, 279; Birt v. Montgomery, 531 F.Supp. 815, 819-20. In each instance, the court found the measures reasonable and justified in light of threats to the lives of Birt and his co-indictees and reports indicating that Birt would attempt to escape during trial. Both the state courts and the district court found that the state trial judge did not abuse his discretion in approving tight security nor did the measures deprive Birt of a fair trial. Upon review of the state court record, we agree with these findings.16 While security at Birt’s trial was unquestionably stringent, we find no deprivation of constitutional rights.
IV. Conclusion
This ease is remanded to the district court for further proceedings to determine whether Birt’s sixth amendment right to counsel of his choice was denied, and whether appointed counsel’s ineffective assistance caused actual and substantial detriment to the conduct of Birt’s defense. If it is determined that Birt was denied the right to *703counsel of his choice, the district court is instructed to issue a writ of habeas corpus discharging Birt from state custody subject to the state’s right to retry him within a reasonable time. If it is determined that appointed counsel’s ineffective assistance caused actual and substantial detriment to Birt’s defense at his state trial, and that such detriment was not harmless beyond a reasonable doubt, the district court is instructed to issue a writ of habeas corpus subject to the conditions previously mentioned.
VACATED and REMANDED.
. The facts of this case are summarized in the published opinion of the Georgia Supreme Court, Birt v. State, 236 Ga. 815, 225 S.E.2d 248, cert. denied, 429 U.S. 1029, 97 S.Ct. 654, 50 L.Ed.2d 632 (1976). Only those facts that are relevant to the issues presented in this appeal are discussed.
. As of the date of oral argument, no resentenc-ing hearing had been scheduled.
. Title 28 U.S.C.A. § 2254(d) provides that:
In any proceeding instituted in a Federal court by an application for a writ of habeas corpus by a person in custody pursuant to the judgment of a State court, a determination after a hearing on the merits of a factual issue, made by a State court of competent jurisdiction in a proceeding to which the applicant for the writ and the State or an officer or agent thereof were parties, evidenced by a written finding, written opinion, or other reliable and adequate written indicia, shall be presumed to be correct, unless the applicant shall establish or it shall otherwise appear, or the respondent shall admit—
(1) that the merits of the factual dispute were not resolved in the State court hearing;
(2) that the factfinding procedure employed by the State court was not adequate to afford a full and fair hearing;
(3) that the material facts were not adequately developed at the State court hearing;
(4) that the State court lacked jurisdiction of the subject matter or over the person of the applicant in the State court proceeding;
(5) that the applicant was an indigent and the State court, in deprivation of his constitutional right, failed to appoint counsel to represent him in the State court proceeding;
(6) that the applicant did not receive a full, fair, and adequate hearing in the State court proceeding; or
(7) that the applicant was otherwise denied due process of law in the State court proceeding;
(8) or unless that part of the record of the State court proceeding in which the determination of such factual issue was made, pertinent to a determination of the sufficiency of the evidence to support such factual determination, is produced as provided for hereinafter, and the Federal court on a consideration of such part of the record as a whole concludes that such fac*694tual determination is not fairly supported by the record:
And in an evidentiary hearing in the proceeding in the Federal court, when due proof of such factual determination has been made, unless i the existence of one or more of the circumstances respectively set forth in paragraphs numbered (1) to (7), inclusive, is shown by the applicant, otherwise appears, or is admitted by the respondent, or unless the court concludes pursuant to the provisions of paragraph numbered (8) that the record in the State court proceeding, considered as a whole, does not fairly support such factual determination, the burden shall rest upon the applicant to establish by convincing evidence that the factual determination by the State court was erroneous.
. Birt testified as follows:
Q: Well your best recollection is that he called you in March or April of ’75?
A: April or March, somewhere, the best I remember.
Q: What did he tell you at that time?
A: He told me that he had been appointed as my attorney on a murder case in that court.
Q: Did you give him any response?
A: Yeah, I told him, I asked him what in the , hell was he talking about, I told him I didn’t, if I wanted an attorney when I got down there I would hire me one. I didn’t want him for no attorney down there in Georgia.
Q: Well did he say anything in response?
A: Well he said he had been appointed by the Judge and uh, he was my attorney. So I told him to go back and inform the Judge that when they brought me to Georgia for arraignment, I would hire me an attorney.
Q: Do you recall what Mr. Collins said in response to that?
A: He said he, he said he would tell the Judge ....
. Birt’s testimony is as follows:
Q: Do you recall how long you spoke with Mr. Collins at the time of the arraignment?
A: I didn’t talk to him none. Judge, went before for the arraignment, Judge told me I appointed this man for attorney and I told the Judge I didn’t want him, I said I don’t want this man for no attorney. I even talked to him on the phone. I told the Judge I didn’t want him. All I wanted to do was make a phone call to my wife and I would hire me an attorney.
Q: What did the Judge say in response, do you recall?
*695A: Judge told me, well he, I appointed this man for your attorney. He is going to be your attorney.
. Collins’s habeas corpus testimony is as follows:
The man had been brought here and I had been appointed and had what I felt like at the time to prepare the case and uh, I didn’t feel like the judge would grant a continuance simply on Mr. Reeves not being prepared. So uh, he wondered what I thought would happen then. I said well I think the case is going to be tried, I think either I’ll try it with your help or you’ll try it with my help, it’s just up to Mr. Birt and what he wants to do. So I was sent out of the room and Mr. Birt and Mr. Reeves had a conference and I was brought back, we talked a few minutes and Mr. Reeves was sent out of the room and Mr. Birt and I had a conference and uh, that conference that I had with Mr. Birt at that time concerned how he would go about uh, getting his retainer or money back from Mr. Reeves if I was going to handle the case. I said I have nothing to do with that Mr. Birt, I don’t know nothing about that, that’s your problem I don’t know. We were both called back in and then a serious discussion became as to who would have the mechanics of getting this case tried. ... The next morning when we came to court, it was agreed that night to with Mr. Birt’s consent, I would be leading counsel so to speak, Mr. Reeves would assist me. So the man would go to trial with an appointed counsel and as retained counsel both working in his interest. When we came to the courtroom, why I was sitting at the table here, Mr. Birt was between us and Mr. Reeves was to his right.
. Birt’s testimony is as follows:
Q: All right, now, isn’t it true that during the, during the trial or prior to the trial that you and Mr. Reeves agreed that even, even though Mr. Reeves had been retained that Mr. Collins would stay on, stay on the case because he knew the people in Jefferson County?
A: No, Mr. Reeves wanted to, wanted to get rid of him.
Q: In other words, if Mr. Collins testified that Mr. Reeves wanted him, that you two agreed that Mr. Collins would be lying, is that what you’re saying?
A: Mr. Reeves wanted me to get rid of him.
Q: What I’m saying is if Mr. Collins comes in this courtroom and testifies that you and Mr. Reeves agreed to let Mr. Collins stay on, uh, that Mr. Collins is wrong and you’re right?
A: No, he would be lying.
Q: All right.
A: I told, I told the Judge, I told Mr. Collins both, I did not want him. Because Mr. Reeves told me that he would do a better job without Mr. Collins. Mr. Reeves told me that. I believe I can do a better job if I don’t have this man, but the Judge put him on me, I couldn’t get rid of him. I mean, I could not get him off.
. Ga.Code Ann. § 38-801(e) was amended in 1980 to provide for statewide service of subpoenas. Acts 1980, pp. 70-71.
. At oral argument, considerable discussion focused on the burden of pleading the fullness and fairness (or lack thereof) of the state court hearing. It is the state’s position that the petitioner has the burden of pleading that the state court hearing was not full and fair, and that such a burden is a prerequisite to a federal court’s consideration of whether to hold another evidentiary hearing. Birt emphasizes that he is not raising the inadequacy of the state factfinding procedures as a constitutional claim. Rather, he claims that Townsend v. Sain, 372 U.S. 293, 83 S.Ct. 745, 9 L.Ed.2d 770 (1963), mandates a federal hearing because of the inadequacy of those procedures. Birt’s federal petition requests the district court, among other things, to “conduct a hearing at which proof may be offered concerning the allegations of this petition.” The state’s answer asserted that Birt had a full and fair hearing in state court and requested the district court to decide the case on the state record, without holding an evidentiary hearing. It is our opinion that both parties have pleaded adequately. Birt requested a hearing; the state countered by alleging that the state hearing was full and fair and therefore no federal hearing was necessary. Because we find that Birt has alleged facts sufficient to justify habeas corpus relief and that the factfinding procedures employed by the state habeas corpus court did not afford a full and fair hearing, we conclude that the district court erred in failing to hold an evidentia-ry hearing.
. The colloquy at the conclusion of the hearing went as follows:
THE COURT: All right. Are there any evidence in rebuttal?
MR. BOGAR: Your Honor, I’m not sure whether the out of town witnesses have arrived.
THE COURT: All right. Mr. Warden, did Mr. Reeves and who was the other witness?
MR. BOGAR: Mrs. Wages.
THE COURT: Mrs. Wages, are they here? Would you check out there and make sure they are not here. Did they indicate they were coming?
MR. BOGAR: We understood that they were under subpoena but we understand that an hour or two ago they may not have been on the way, suggest they might not get here. Your Honor, at this time we would like to renew our motion on our experts, investigators based on our showing that we’ve made. We would like to renew our motion for discovery as well to just particularly your Honor, in respect to these two witnesses that didn’t arrive that might be appropriate in view of the limited funds of the Petitioner has had to work with that we be given a short period to put in an affidavit from either of these witnesses the possibility of a counter affidavit by the State.
THE COURT: What does the State wish to say in response?
MR. DUNSMORE: Well, your Honor, these witnesses weren’t subpoenaed and, of course, this is all in the discretion of the court. We would oppose, but we will defer to whatever the court will do.
MR. BOGAR: These witnesses are under subpoena.
MR. DUNSMORE: Well I don’t know whether the funds were given to them to the question whether it’s a valid subpoena or not.
THE COURT: Were funds given to them? And Lawrenceville is more than 150 miles radius.
MR. BOGAR: I believe that’s correct. It’s more than a 150 miles.
THE COURT: Well the court is going to conclude the hearing but uh, the record will so note the objection made to it....
. The state habeas corpus court found that Birt personally relinquished his right to challenge the composition of the grand jury, a finding affirmed on appeal. Birt v. Hopper, 245 Ga. 221, 223, 265 S.E.2d 276, 278. Birt apparently acquieses in this finding because he raises no grand jury challenge in his federal petition.
. Census figures reveal that blacks represented 54.5% of the Jefferson County population and that women represented 52.5%. The traverse jury pool was made up of 21.6% blacks and 34.9% women. The actual jury that tried Birt was composed of three white males, five white females, three black males, and one black female.
. On the September 1970 pool, the statistical disparity of blacks was 42.7%, of women 50.7%. On the January 1972 pool, the disparity of blacks was 42.5%, disparity of women was 49.2%. On the March 1975 pool, disparity of blacks was 40%, disparity of women 47.7%.
. Commissioner McGahee explained the process by which the jury lists were revised to remedy underrepresentation:
A: We took the voter registration list and went right back over it like we did before and just added on, tried in our own mind of the people that we knew from the districts that we had, to uh, to put what we thought would be an average pro rata share and I thought of blacks, females and teenagers, with no, no given percentage in mind.
Q: Well pro rata share meant what to you?
A: Just as I stated, what we thought would be the logical thing to do.
Q: Okay, what do you mean, what would be the logical thing to do?
A: Well from the voter registration list that we had, we picked people that we though were suitable and would do a good job as a juror.
. We do not mean to imply that counsel, in order to render constitutionally effective assistance, need investigate and challenge jury compositions in every case. We only point out that when such investigation is undertaken, it should be performed with a sufficient degree of background knowledge regarding population percentages and Supreme Court guidelines in this area of law. It is this lack of investigation, coupled with an apparently prima facie case of unconstitutional composition which we find inexcusable in this case.
. The restrictive subpoena range statute discussed in section III.A. of this opinion prevented the compelled attendance of certain Georgia Bureau of Investigation (GBI) officials subpoenaed by Birt to testify at the state habeas corpus hearing. Birt sought to demonstrate by their testimony that the concern over threats and attempted escapes was unfounded. Because we conclude that the security measures employed were not unnecessarily excessive, we need not address Birt’s challenge to Ga.Code Ann. § 38-801(e) (revised and recodified at section 24-10-21 (1982)) as it relates to the GBI officials.