Remanded by published opinion. Judge WILLIAMS wrote the opinion, in which Judge FLOYD concurred. Judge MICHAEL wrote a separate opinion concurring in the judgment and concurring in part.
OPINION
WILLIAMS, Circuit Judge.Curtis Delmont Woolfolk pleaded guilty to one count of possession with intent to distribute more than five grams of crack cocaine, in violation of 21 U.S.C.A. § 841(a)(1) (West 1999), while reserving the right to challenge his prosecution as violating the Speedy Trial Act, 18 U.S.C.A. § 3161(b) (West 2000) and his Sixth Amendment right to a speedy trial. The district court rejected both of Woolfolk’s claims, and, for the following reasons, we remand the case to the district court for further proceedings. We remand for further consideration of whether Woolfolk was subject to “any restraint resulting from federal action” that triggered the Speedy Trial Act’s provisions. ■ United States v. Lee, 818 F.2d, 302, 305 (4th Cir.1987). Because of the factual uncertainty regarding Woolfolk’s detention, we also remand the case for a full consideration of Woolfolk’s Sixth Amendment claim under Barker v. Wingo, 407 U.S. 514, 92 S.Ct. 2182, 33 L.Ed.2d 101 (1972).
I.
On December 15, 2002, Detective David Harris was assigned to a sobriety checkpoint in downtown Charlottesville, Virginia. At approximately 2 a.m., a 1991 Lincoln approached the checkpoint and turned into another lane in an effort to avoid it. Detective Harris began a pursuit of the vehicle and effected a stop. Harris approached the ear and observed that the *593driver of the vehicle, Woolfolk, appeared to be intoxicated. Harris also had personal' knowledge that Woolfolk was involved in drug activities. ■ During the traffic stop, several Charlottesville residents who had been standing nearby watching the stop approached Woolfolk’s vehicle and attempted to gain entry. ' Harris heard Woolfolk tell one such individual that “it[’]s between the seats.” (J.A. at 6.) Woolfolk was arrested for driving under the influence. Following .the arrest, Harris performed a search of the vehicle and found eight grams of crack cocaine in the center console.1
On December 18, 2002, the United States (the Government) filed a .criminal complaint against Woolfolk in the United States District Court for the Western District of Virginia, alleging that Woolfolk knowingly possessed with-intent to distribute five grams or more of crack cocaine, in violation of 21 U.S.C.A. § 841(a)(1). An arrest warrant for Woolfolk was issued on the same date. At the time, Woolfolk was in the custody of Virginia authorities pending trial on state charges stemming from the December 15 arrest.2 On January 9, 2003, the Government issued a federal de-tainer to the state authorities. The detain-er specified that a federal arrest warrant had been issued against Woolfolk. The detainer also requested that “[p]rior to the subject’s release from your custody, please notify this office at once so that we may assume custody if necessary.” (J.A. at 13.) The detainer also was to be served on Woolfolk, but he contends that he received the warrant but not the detainer.
Although Woolfolk’s state proceedings were terminated on April 10, 2003, Wool-folk was not released by the state authorities at that time.3 The record contains no evidence as to why the state continued to detain Woolfolk after April 10. At a hearing before the district court on Woolfolk’s motion' to dismiss, Woolfolk contended that, after April 10, “there can be no other interpretation” of the record but that Woolfolk was being held only because of the federal detainer. (J.A. at 22.) The district court responded, “[t]hat seems to be conceded, that the only thing keeping him in jail was a federal detainer.” (J.A. at 22.) Woolfolk answered that question in the affirmative, and the Government did not respond. On appeal, however, the Government contends that Virginia failed, as an administrative matter, properly to process the termination of Woolfolk’s state charges and therefore was holding him on the dismissed state charges instead of the federal detainer.
Although it remains unclear why Wool-folk remained in state custody, at some point, apparently after Woolfolk filed a state habeas claim, the Government became aware that Woolfolk was still in state custody even though no proceedings remained against him in the state system. *594At oral argument before the district court, the Government asserted that “[w]hen [Woolfolk’s] situation was brought to [the Government’s] attention, [it] brought him over federally and executed the complaint.” (J.A. at 21.) This action occurred on July 10, 2003, when the Government executed its December 18 arrest warrant and brought Woolfolk before a magistrate judge for his initial appearance. On August 7, the federal. grand jury indicted Woolfolk on one count of violating § 841(a)(1).
On August 22, Woolfolk filed a motion to dismiss the indictment, alleging that the delay between the filing of the complaint and arrest warrant and serving of the detainer and the indictment violated the Speedy Trial Act, 18 U.S.C.A. § 3161(b), and his Sixth Amendment rights to a speedy trial. The district court heard arguments on the dismissal motion and, on October 2, 2003, issued an order denying it. Woolfolk subsequently entered a conditional guilty plea, which reserved his right to appeal the district court’s denial of the dismissal motion. Woolfolk was sentenced to sixty months imprisonment on March 12, 2004, and filed a timely appeal on March 18. We have jurisdiction pursuant to 28 U.S.C.A. § 1291 (West 1999).
II.
On appeal, Woolfolk contends that the Government’s delay in indicting him violated both the Speedy Trial Act and the Sixth Amendment and that accordingly, the district court erred in failing to grant his motion to dismiss. We address each argument in turn.
A. Speedy Trial Act
We review the district court’s factual findings on a motion to dismiss an indictment for clear error, but we review 'its legal conclusions de novo. United States v. Good, 326 F.3d 589, 591 (4th Cir.2003). The Speedy Trial Act provides, in relevant part, that “[a]ny information or indictment charging an individual with the commission of an offense shall be filed within thirty days from the date on which such individual was arrested or served with a summons in connection with such offense.”4 18 U.S.C.A. § 3161(b). If the Government fails to comply with this requirement, the “complaint shall be dismissed or otherwise dropped.” 18 U.S.C.A. § 3162(a)(1). We have interpreted this language to provide that the Government must charge a defendant by indictment or information within 30 days of his “federal arrest upon a federal charge” or face the prospect of dismissal. United States v. Thomas, 55 F.3d 144, 148 (4th Cir.1995) (quoting United States v. Lee, 818 F.2d 302, 305 (4th Cir.1987)). The Act “is intended to mandate an orderly and expeditious procedure for federal criminal prosecutions by fixing specific, mechanical time limits within which the various progressions in the prosecution must occur.” United States v. Iaquinta, 674 F.2d 260, 264 (4th Cir.1982).
On appeal, Woolfolk argues that the provisions of the Speedy Trial Act were triggered on January 9, when the Government lodged a detainer against him with the state because, on that date, the Government had issued a complaint, served an arrest warrant, and lodged a detainer with the state. In the alternative, Woolfolk contends that the Act’s 30 day time limit began on April 10, when the state concluded its prosecution but continued holding him, allegedly because of the federal de-tainer. The Government counters that *595Woolfolk was not subject to “federal arrest” or “federal custody on a federal charge,” see Thomas, 55 F.3d at 148,, until July 10, when the magistrate judge issued the temporary detention order. With July 10 as the starting date, the Government notes, the August 7 indictment complies with the dictates of the Act.5
Woolfolk’s contention that the protections of the Speedy Trial Act were triggered on January 9 is foreclosed by our holding in Thomas. In Thomas, state authorities were detaining the defendant on state charges when the Government filed'a criminal complaint, secured an arrest warrant, and lodged the arrest warrant as a detainer with the state authorities. Id. at 147. Thomas remained in the custody of state authorities facing state charges for more than two years. Id. The state authorities concluded their prosecution, and the Government indicted Thomas within thirty days of the termination of the state prosecution. Id. We rejected Thomas’s argument that the complaint, warrant and detainer activated the requirements of the Speedy Trial Act, finding that, when an individual is lawfully being held to answer to state charges, a “criminal complaint coupled with an unexecuted arrest warrant and a federal detainer” do not trigger the Act. Thomas, 55 F.3d at 148. See also Lee, 818 F.2d at 303 (finding that the Act requires a federal arrest upon a federal charge and rejecting defendant’s argument that filing of complaint, arrest warrant and detainer on individual .being held in state custody on state charges constituted a federal arrest on a federal charge).6 Accordingly, under the binding precedent of Thomas, the Government’s filing of a complaint, serving of an arrest warrant, and lodging of that warrant as a detainer on January 9, while Woolfolk .was in state custody answering to state charges, did not activate the provisions of the Speedy Trial Act.
Woolfolk’s second argument, that the Speedy Trial Act’s thirty-day time limit for ‘filing an indictment began on April 10, when his state proceedings terminated but his detention continued, gives us some pause. Neither Thomas nor Lee specifically address that argument. In both of those cases, the federal indictment was filed within thirty days of the termination of the state proceedings. Here, the state proceedings terminated on April 10, but the federal indictment was not filed until August 7. In fact, we have found no case-law that addresses the specific factual situation before us. A canvas of our caselaw in this area, however, does provide us guidance on how to proceed in'this case. First, as Thomas makes clear, for the Act to apply, the defendant must be under “federal arrest” or be in “federal custody.” The relevant question thus’ becomes whether an individual being held by state authorities is ever under “federal arrest” or in “federal custody.” The answer, at least while a state has valid charges cur*596rently pending against an individual, is “no.” We believe however, that in limited circumstances, this question can be answered in the affirmative. In Iaquinta, we cited, with approval, the following passage from a law review article-.
For this [thirty-day time] limit to commence, a person must be held for the purpose of answering to a federal charge. Thus, if one is held by state officers on a state charge and subsequently turned over to federal authorities for federal prosecution, the starting date of the time period is the date that the defendant is delivered into federal custody. However, if the person is held in state custody at the request of federal authorities, the date of arrest by the state officers is controlling.
Iaquinta, 674 F.2d at 267 (quoting Martoche, The Federal Speedy Trial Act: An Introduction and Guide, 4 Nat. Journal of Criminal Def. 295 (1978)) (emphases added). In Lee, we again quoted, with approval, the suggestion that “[f]or the time limit of the Act to commence a person must be held for the purpose of answering a federal charge.” Lee, 818 F.2d at 304 (quoting United States v. Shahryar, 719 F.2d 1522, 1524-25 (11th Cir.1983) (emphasis in original)). We then reiterated that “to the knowledge of this Court, [no] other Court [has] stated — that a federal complaint without federal arrest or any restraint resulting from federal action brings the combination of 18 U.S.C. §§ 3161(b) and 3162(a)(1) into play.” Id. at 305 (emphasis added). Thus, Lee makes explicit that the provisions of the Speedy Trial Act can be triggered by something other than actual federal custody and federal arrest, i.e., “any restraint resulting from federal action.” Id. Although Lee does not discuss the parameters of this language, we believe that a “restraint resulting from federal action,” sufficient to trigger the time limits of the Speedy Trial Act, occurs when the Government has knowledge that an individual is held by state authorities solely to answer to federal charges.7
The phrase “federal action,” in our view, requires a showing that the Government knew or should have known that the defendant was restrained solely to answer federal charges. Permitting-the Speedy Trial Act’s provisions to apply whenever a state has concluded its prosecution but failed to notify the Government would be an undesirable result. Given the breadth of the Government’s criminal prosecutions, and what must be the sheer number of federal detainers lodged with state authorities, to impose a form of strict liability upon the Government for actions taken by independent sovereigns would be detrimental to the administration of justice. Instead, the Speedy Trial Act’s purpose is best served if its provisions are triggered in those instances where the Government has knowledge that an individual is being held by state authorities only to answer to federal charges. In such situations, we believe an individual would be subject to a “restraint resulting from federal action.” Id.
Applying this rule to the facts before us, we believe a remand to the district court is necessary. First, it is unclear whether, after April 10, Woolf oik remained in state custody only to answer to federal charges. On remand, the district court should consider whether the state continued to hold Woolfolk because of the federal detainer, *597or because, as the Government alleges before this court, the state failed to process the termination of Woolfolk’s ■ state charges. Moreover, even if we assume that Woolfolk was being held by the state solely because of the federal detainer from April 10 to July 10, thus making him subject to a “restraint” during that period, it is not clear, on the facts as currently developed, that the restraint was a result of “federal action.” The record does not show when the Government knew or should have known that Woolfolk was being held solely because of the federal de-tainer.
In sum, we must remand the case for the district court to determine when the Government knew or should have known that Woolfolk was being held by the state solely because of the federal detainer. If the Government knew or should have known before July 8, then the Government violated the Act, and Woolfolk’s indictment should be dismissed.
B. Sixth Amendment Speedy Trial Rights
Woolfolk next argues that his Sixth Amendment rights were violated by the delay following the issuance of. the federal detainer on January 9. The Sixth Amendment provides that “[i]n all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial.” U.S. Const, amend. VI. In order to prove a Sixth Amendment violation in this context, a defendant “must show first that the Amendment’s protections have been triggered by ‘arrest, indictment, or other official accusation.’ ” Thomas, 55 F.3d at 148 (quoting Doggett v. United States, 505 U.S. 647, 655, 112 S.Ct. 2686, 120 L.Ed.2d 520 (1992)).
If the Sixth - Amendment protections apply, we must make “four separate [inquiries: whether delay before trial was uncommonly long, whether the government or the criminal defendant is more to blame for that delay, whether, in due course, the defendant asserted his right to a speedy trial, and whether he suffered prejudice as the delay’s result.”8 Doggett, 505 U.S. at 651, 112 S.Ct. 2686. In addition to being a factor, the first inquiry is also a threshold requirement, because “[sjimply to trigger a speedy trial analysis, an accused must allege that the interval between accusation and trial has crossed the threshold dividing ordinary from presumptively prejudicial delay.” Id. at 651-652, 112 S.Ct. 2686 (quotation marks omitted). After the defendant makes this threshold showing, he “must ... show on balance,” that the four inquiries weigh in his favor. Thomas, 55 F.3d at 148.
Under Thomas, the filing of the detainer, warrant and complaint on January 9, 2003, triggered Woolfolk’s Sixth Amendment speedy trial rights. See Thomas, 55 F.3d at 149 (holding that “the combination of the criminal complaint, the arrest warrant, and the federal detainer were sufficient to implicate the speedy trial provision of the Sixth Amendment”). He was indicted on August 7, almost eight months later, and pleaded guilty on December 19, almost a full year after his Speedy Trial rights attached.
The Supreme Court has counseled, that “postaccusation delay [is] presumptively prejudicial at least as it approaches one year.” Doggett, 505 U.S. at 652 n. 1, 112 S.Ct. 2686. One year is the “point at which courts deem the delay unreasonable enough to trigger the Barker [i]nquiry.” *598Id. The Supreme Court, however, has never offered guidance on what the phrase “postaccusation delay” encompasses, and in this case it is unclear whether the time from January 9 to December 19, or from January 9 to August 7, is the proper measure.9 Even assuming, however, that the relevant period of “postaccusation delay” is the period from the serving of the detain-er, arrest warrant, and complaint on January 9 to the filing of the indictment on August 7, we believe that Woolfolk has met the threshold Barker requirement. As one commentator explains, “it may generally be said that any delay of eight months or longer is presumptively prejudicial.” 4 Wayne R. LaFave, Jerold H. Israel, & Nancy J. King, Criminal Procedure § 18.2(b)(2d ed.1999) (quoting Joseph, Speedy Trial Rights in Application, 48 Fordham L. Rev. 611, 623 n. 71 (1980)). Although the eight month threshold is a general rule and not a rigid requirement, see United States v. Cope, 312 F.3d 757, 778 (6th Cir.2002) (finding eight month delay was “substantial” but not “presumptively prejudicial” in “two-defendant, eleven-count case that involves multiple allegations of attempted murder”), given the fact that Woolfolk’s case involves little complexity, we see no reason to deviate from that general rule here. Thus, regardless of whether the relevant period of postaccu-sation delay is from January 9 to August 7 or from January 9 to December 19, the postaccusation delay in this case was presumptively prejudicial and Woolfolk has satisfied the threshold Barker requirement.
Although Woolfolk has satisfied the threshold requirement, that fact by no means ends our Barker inquiry. We have previously found no Sixth Amendment violation in cases involving time periods much greater than that at issue here. See United States v. Grimmond, 137 F.3d 823, 827 (4th Cir.1998) (thirty-five months); Thomas, 55 F.3d at 149-150 (two and a half years). At this stage in the analysis, we typically would examine the remaining Barker inquiries in order to determine if Woolfolk’s Sixth Amendment rights were violated. On the record before us, however, we believe that a remand to the district court is more appropriate. The Barker inquiry is a “fact-intensive inquiry,” Cope, 312 F.3d at 778, and, given the uncertainty regarding the cause of Woolfolk’s detention after April 10, we believe that the district court is in the best position to conduct a full Barker analysis.
III.
For the foregoing reasons, we remand the case to the district court for further consideration of Woolfolk’s Speedy Trial Act and Sixth Amendment claims.
REMANDED.
. Although the record is unclear, Woolfolk apparently was taken into custody by Virginia authorities following this arrest. According to the limited record in this proceeding, Woolfolk was charged by Virginia with four violations of state law stemming from the December 15, 2002 arrest — driving under the influence, manufacture of a controlled substance, refusal, and driving on a suspended operator’s license.
. Although we recognize that Virginia is a commonwealth, we use the familiar term “state" in lieu of "Commonwealth of Virginia.”
. One of the charges against Woolfolk was nolle prossed on February 20, 2003. On April 10, 2003, Woolfolk was found guilty of the charge of driving on a suspended operator's license and was given a suspended sentence of ten days imprisonment. Also on April 10, the remaining two state charges were nolle prossed.
. Woolfolk contends that he was "arrested” within the meaning of § 3161(b) but does not argue that he was "served with a summons.” 18 U.S.C.A. § 3161(b) (West 2000).
. The district court found that Woolfolk was never in federal custody before his indictment. This conclusion is erroneous because, at a minimum, Woolfolk was in federal custody as of July 10, 2003 when the arrest warrant was executed and Woolfolk was transferred to federal custody.
. The basis for the holding in Thomas and Lee is the notion of dual sovereignty, "which recognizes that 'the federal government is not bound by the actions of state authorities and that successive state and federal prosecutions are constitutionally permissible.’.” ■ United States v. Iaquinta, 674 F.2d 260, 264 (4th Cir.1982) (quoting United States v. Wilson, 657 F.2d 755, 767 (5th Cir.1981)). As another circuit has explained, "one sovereign's actions should not force the other sovereign to proceed with a prosecution before it is ready.” United States v. Benitez, 34 F.3d 1489, 1493 n. 1 (9th Cir.1994).
. The language used in Lee is analogous to the “ruse” exception adopted in other circuits. See, e.g., United States v. Cepeda-Luna, 989 F.2d 353 (9th Cir.1993). Under the ruse exception, "Speedy Trial Act time periods may be triggered by state detentions that are merely a ruse to detain the defendant solely for the purpose of bypassing the requirements of the Act.” United States v. Benitez, 34 F.3d 1489, 1494 (9th Cir.1994).
. This four part balancing test was originally set forth in Barker v. Wingo, 407 U.S. 514, 92 S.Ct. 2182, 33 L.Ed.2d 101 (1972), and is commonly referred to as the Barker balancing test.
. Although Woolfolk’s motion to dismiss seemed to target the delay from the serving of the detainer through his impending trial, before this court Woolfolk has centered his Sixth Amendment claim on the delay between the filing of the complaint, warrant, and de-tainer and his indictment, not between the indictment and trial or even the filing of the complaint, warrant, detainer and trial.