Vasquez v. Guerrero and the Objective “Reasonable Attorney” Standard for AEDPA Due Diligence in Successive Habeas Petitions

I. Introduction

The Fifth Circuit’s unpublished, per curiam decision in Vasquez v. Guerrero, No. 25‑70005 (5th Cir. Dec. 4, 2025), arises from a Texas capital case in which Richard Vasquez sought to file a successive federal habeas petition based on allegedly flawed cocaine toxicology evidence used at his trial.

The opinion does not create new doctrine from whole cloth, but it crystallizes and applies several powerful strands of post‑AEDPA jurisprudence:

• AEDPA’s due diligence requirement for successive petitions under 28 U.S.C. § 2244(b)(2)(B)(i) is objective and is measured by what a reasonable attorney could have discovered at the time of the first federal habeas petition, not by the subjective diligence of the actual petitioner.
• This “reasonable attorney” standard applies even when the successive claim is itself an ineffective assistance of counsel claim under Strickland v. Washington.
• Under Shinn v. Ramirez and related authority, federal courts lack equitable power to create exceptions to AEDPA’s statutory gatekeeping—even for compelling or sympathetic cases; attorney error in postconviction proceedings is imputed to the petitioner.
• Even if due diligence were assumed, the stringent innocence prong of § 2244(b)(2)(B)(ii) was not met; the non‑cocaine evidence of intent to kill was independently strong.

For practitioners, especially in capital litigation, Vasquez is a stark illustration of how unforgiving AEDPA’s successive‑petition regime is, and how little room remains for late‑developed expert critiques of trial evidence when the underlying records have long been available.

II. Factual and Procedural Background

A. The Underlying Crime and Trial

In 1998, Richard Vasquez lived with his girlfriend, Brenda Lopez, their infant daughter Meagan, and Brenda’s four‑year‑old daughter from a prior relationship, Miranda. Both adults were heavily addicted to drugs. On March 5, 1998, after injecting heroin, Vasquez drove Brenda to work with the children in the backseat. He became angry about having to watch the children and being unable to obtain more drugs.

After dropping Brenda off and returning home with the children, Vasquez called 911 a few hours later, claiming Miranda was choking. Responding paramedics observed a bump on Miranda’s head, bruises on her back, and bruising around her eyes, suggesting serious head trauma. Miranda later died from her injuries.

The State charged Vasquez with capital murder under Tex. Penal Code § 19.03(a)(8), alleging that he intentionally or knowingly caused Miranda’s death by striking her head with his hand. Under Texas law, the State had to prove that Vasquez either:

• acted with the conscious objective or desire to cause death, or
• was aware that his conduct was reasonably certain to cause death. (Tex. Penal Code §§ 6.03(a)–(b), 19.02(b)(1)).

At trial, Vasquez admitted he struck Miranda but claimed her fatal injuries came from her falling off a stool. The evidence, however, showed:

• Extensive physical trauma: “At least 20 to 30” areas of contusion on Miranda’s body (face, head, trunk, etc.).
• Evidence suggestive of sexual assault (perineal injuries consistent with severe assault and restraint).
• Cocaine in Miranda’s system, at allegedly toxic levels.

The State used this evidence to prove the mens rea element, arguing that:

1. Miranda’s head injuries were comparable to those seen in a high‑speed vehicular ejection.
2. Her perineal injuries suggested severe sexual assault, which could provide a motive to silence her.
3. She had a lethal amount of cocaine in her system, allegedly administered by Vasquez, which supported both brutality and awareness of the risk of death.

The cocaine evidence came from three sources:

• Dr. Backer, whose laboratory performed the toxicology testing and produced the Toxicology Report. He testified that testing showed a toxic amount of cocaine introduced an hour or two before hospital admission.
• Dr. White, the medical examiner, who relied on the Toxicology Report and listed cocaine intoxication as a contributing cause of death in the autopsy report.
• The Toxicology Report itself, admitted as part of Miranda’s medical records.

Vasquez denied giving Miranda cocaine and denied any sexual assault. Nonetheless, the jury convicted him of capital murder and he was sentenced to death. The Texas Court of Criminal Appeals (TCCA) affirmed on direct appeal, and earlier federal proceedings (see Vasquez v. Thaler, 389 F. App’x 419 (5th Cir. 2010)) upheld the conviction and sentence.

B. Initial Post‑Conviction Proceedings

Vasquez’s initial state and federal habeas petitions did not challenge the cocaine evidence. Those earlier postconviction attacks focused on other theories. In 2015, after Texas enacted Article 11.073 (allowing claims based on “new scientific evidence”), Vasquez filed a new state habeas application, largely focused on evidence regarding Miranda’s head trauma.

C. The 2019 Toxicology Discovery

While preparing for an Article 11.073 state evidentiary hearing in April 2019, Vasquez’s counsel retained a consulting toxicologist, Dr. Valentine, to explore how cocaine could have entered Miranda’s system. Upon reviewing the Toxicology Report, Dr. Valentine discovered an apparent inconsistency:

• The report’s preliminary “drugs of abuse” screen—designed to detect the presence of common drugs—was marked “negative.”
• Despite this, the report reflected further testing that purportedly showed a high quantity of cocaine in Miranda’s blood.

Ordinarily, a “negative” screen would suggest no detectable drugs and therefore no need for confirmatory quantification. This discrepancy prompted counsel to re‑contact Dr. Backer and Dr. White. Both experts recanted or significantly retreated from their trial testimony:

• Dr. Backer stated that the Toxicology Report and his trial testimony were “not reliable evidence.”
• Dr. White stated that he would have insisted on a second toxicology report to verify the result.

Although there was a negative initial screen, the report still showed a subsequent test with a high cocaine level; the Fifth Circuit later notes this to underscore that the cocaine evidence was not entirely eliminated by the new critique.

D. Later State Proceedings and the Successive Federal Petition

Vasquez filed a new state habeas application focused on the cocaine evidence, but the TCCA dismissed it on procedural grounds in 2022. He then turned to federal court.

In February 2023, he sought authorization from the Fifth Circuit under 28 U.S.C. § 2244(b)(3)(A) to file a successive § 2254 petition. His proposed petition contained nine claims; the Fifth Circuit, in In re Vasquez, No. 23‑40079 (5th Cir. June 23, 2023), granted authorization only as to three:

• Claims 1 and 2: “actual innocence” arguments.
• Claim 6: an ineffective assistance of counsel claim based on trial counsel’s failure to discover the flaws in the cocaine evidence.

The panel specified that the innocence claims were authorized only as a “gateway” to allow consideration of Claim 6, not as stand‑alone merits claims.

Back in district court, the State moved to dismiss, arguing that Vasquez failed to meet AEDPA’s prerequisites for successive petitions under 28 U.S.C. § 2244(b)(2)(B). The district court independently reviewed the case—as required by § 2244(b)(4)—and held that Vasquez had not satisfied the due diligence requirement in § 2244(b)(2)(B)(i). It therefore dismissed the petition without reaching the underlying ineffective assistance allegations, but granted a certificate of appealability (COA) on that procedural issue. Vasquez appealed.

III. Summary of the Opinion

On appeal, the Fifth Circuit:

1. Held that it had jurisdiction under 28 U.S.C. § 2253(c)(1), and, even if the district court’s COA were technically defective, the court would issue a valid COA in its place (citing Wallace v. Mississippi, 43 F.4th 482 (5th Cir. 2022), and United States v. Castro, 30 F.4th 240 (5th Cir. 2022)).
2. Reviewed the dismissal of the successive petition de novo, treating AEDPA compliance as a legal question.
3. Affirmed the district court’s ruling that Vasquez failed to satisfy § 2244(b)(2)(B)(i)’s due diligence requirement, because:
   • The Toxicology Report and conflicting trial testimony were available well before his first federal habeas petition in 2006.
   • A “reasonable attorney” would have been put on notice of the inconsistency and could have investigated it then.
4. Rejected Vasquez’s argument that the diligence standard should shift from a reasonable attorney to a “reasonable petitioner” in the context of ineffective assistance claims.
5. Rejected his request for an equitable exception to AEDPA’s diligence requirement, relying heavily on Shinn v. Ramirez, 596 U.S. 366 (2022), to hold that:
   • Postconviction counsel’s errors are imputed to the petitioner.
   • Congress’s statutory limitations in AEDPA admit no judge‑made equitable exceptions.
6. Additionally (and independently) held that Vasquez failed to satisfy § 2244(b)(2)(B)(ii)’s innocence requirement, because:
   • Even discounting the cocaine evidence, the remaining evidence of intent—severe head trauma and sexual‑assault evidence—was independently powerful.
   • The new toxicology critique did not show, by clear and convincing evidence, that no reasonable factfinder would have found Vasquez guilty.

Accordingly, the panel affirmed the dismissal of the successive petition, and denied as moot a motion carried with the case.

IV. AEDPA’s Successive Petition Framework

The opinion is anchored in the structure of 28 U.S.C. § 2244(b), which governs successive federal habeas petitions:

• First gate – court of appeals authorization (§ 2244(b)(3)): Before filing a successive § 2254 petition in district court, a prisoner must obtain authorization from the court of appeals. The court of appeals only determines whether the petitioner has made a prima facie showing that he may satisfy § 2244(b)(2).
• Second gate – district court’s independent review (§ 2244(b)(4)): Even after authorization, the district court must independently verify that the statutory criteria are actually met; the court of appeals’ authorization is “tentative.”

For claims based on newly discovered facts, § 2244(b)(2)(B) requires:

1. Due diligence: “the factual predicate for the claim could not have been discovered previously through the exercise of due diligence” (§ 2244(b)(2)(B)(i)); and
2. Innocence: “the facts underlying the claim, if proven and viewed in light of the evidence as a whole, would be sufficient to establish by clear and convincing evidence that, but for constitutional error, no reasonable factfinder would have found the applicant guilty” (§ 2244(b)(2)(B)(ii)).

Failure to satisfy either prong requires dismissal. In Vasquez, the Fifth Circuit finds that both prongs are unsatisfied but focuses primarily on diligence.

V. Precedents Cited and Their Role in the Decision

A. Johnson v. Dretke and Williams v. Taylor – The “Reasonable Attorney” Lens

The central interpretive foundation is Johnson v. Dretke, 442 F.3d 901 (5th Cir. 2006). Johnson alleged a Brady violation: the prosecution allowed his accomplice to testify while suppressing a stipulation in which the accomplice confessed to the murder. The Fifth Circuit held Johnson did not satisfy § 2244(b)(2)(B)(i) because a reasonable attorney would have been on notice of, and able to discover, that stipulation earlier.

In Johnson, the court derived this standard from the Supreme Court’s diligence analysis in Williams v. Taylor, 529 U.S. 420 (2000). There, in interpreting a different AEDPA provision, the Supreme Court evaluated whether anything in the record would have put a “reasonable attorney” on notice of alleged misconduct. The Fifth Circuit in Vasquez explicitly invokes this chain:

• Congress used the passive voice in § 2244(b)(2)(B)(i) (“could not have been discovered”), indicating an objective, impersonal standard, not the subjective diligence of a particular lawyer or petitioner.
• This objective standard aligns with evaluating what a reasonable attorney could have discovered at the time of the first federal petition.

Since Johnson, the Fifth Circuit has repeatedly applied this approach, and Vasquez treats it as the controlling interpretation of § 2244(b)(2)(B)(i).

B. In re Davila, Blackman v. Davis, Swearingen, Will, Carty, and Cantu – Refining “Notice” and Diligence

The opinion references several Fifth Circuit cases that operationalize the diligence inquiry by focusing on what would have put a person or attorney on notice of the relevant factual predicate:

• In re Davila, 888 F.3d 179 (5th Cir. 2018): Emphasizes the “two gates” framework and states that the diligence question asks whether due diligence “at the time of the first habeas petition” would have led to discovery of the new factual basis.
• Blackman v. Davis, 909 F.3d 772 (5th Cir. 2018): Applies the Johnson approach, asking whether “evidence … would have put a reasonable attorney on notice” of the potential claim.
• In re Swearingen, 935 F.3d 415 (5th Cir. 2019); In re Will, 970 F.3d 536 (5th Cir. 2020); In re Carty, 824 F. App’x 271 (5th Cir. 2020): These cases variously frame the standard in terms of what a “reasonable person” or “petitioner” could have known, but still emphasize objective notice, not subjective ignorance.
• In re Cantu, 94 F.4th 462 (5th Cir. 2024): Explicitly considers whether an “objectively diligent attorney” could have conducted the relevant investigation during the initial habeas proceeding.

Vasquez acknowledges that its prior cases have used slightly different formulations—“reasonable attorney,” “reasonable person,” “reasonable petitioner”—but holds that any such differences are immaterial here because Vasquez fails under any objective standard. Nonetheless, for represented prisoners like Vasquez, the court squarely re‑affirms the reasonable attorney benchmark as the operative lens.

C. Shinn v. Ramirez, In re Coleman, Martinez v. Ryan, and Irving v. Hargett – No Equitable Exceptions, and Imputing Counsel’s Errors

The panel’s rejection of any equitable exception to AEDPA’s diligence requirement relies heavily on the Supreme Court’s decision in Shinn v. Ramirez, 596 U.S. 366 (2022). In Shinn, the Court held:

• A prisoner has no constitutional right to counsel in state postconviction proceedings.
• Consequently, the prisoner generally bears responsibility for all attorney errors in those proceedings.
• Courts cannot graft Martinez v. Ryan‑style equitable exceptions onto AEDPA’s statutory limits on evidentiary development (there, § 2254(e)(2)); “Congress foreclosed” this by enacting AEDPA.

The Vasquez panel analogizes this logic to § 2244(b)(2)(B)(i): Congress’s command is statutory, not judge‑made, and federal courts “have no authority to amend” AEDPA to excuse lack of diligence, even in hard cases.

The court also cites:

• In re Coleman, 768 F.3d 367 (5th Cir. 2014): Observes that § 2244(b)(2)(B) will often foreclose ineffective assistance claims in successive petitions because the dual requirements (unavoidability plus clear‑and‑convincing innocence) and Strickland’s own prejudice requirement are hard to reconcile in a later‑discovered‑evidence situation.
• Martinez v. Ryan, 566 U.S. 1 (2012): Recognized an equitable “cause” exception to excuse state procedural default where ineffective assistance of trial counsel must be raised in an initial‑review collateral proceeding and postconviction counsel is ineffective. Vasquez emphasizes, via Shinn, that Congress has foreclosed extending such equitable doctrines to AEDPA’s statutory bars.
• Irving v. Hargett, 59 F.3d 23 (5th Cir. 1995): Earlier, pre‑AEDPA authority for the proposition that prisoners bear responsibility for the acts and omissions of counsel in collateral proceedings.

The core message is that postconviction counsel is the prisoner’s agent; when counsel fails to uncover a claim that could have been found with reasonable diligence, the prisoner is bound by that failure in subsequent successive‑petition litigation.

D. Brady, Giglio, Napue, and Strickland – Substantive Claims vs. Procedural Gatekeeping

The opinion also references the classic criminal procedure cases:

• Brady v. Maryland, 373 U.S. 83 (1963): Prosecution’s duty to disclose material exculpatory evidence.
• Giglio v. United States, 405 U.S. 150 (1972) and Napue v. Illinois, 360 U.S. 264 (1959): Prohibit the knowing use of false or misleading testimony by the State.
• Strickland v. Washington, 466 U.S. 668 (1984): Governs ineffective assistance of counsel claims, requiring deficient performance and prejudice.

Vasquez argued that due diligence should be assessed differently for Strickland‑based successive claims than for Brady/Giglio/Napue claims, because the underlying wrong is counsel’s own failure rather than prosecutorial misconduct. The panel flatly rejects this, emphasizing:

• § 2244(b)(2)(B)(i) speaks in general terms, “without limitation to any specific claim” (paralleling the Supreme Court’s reading of § 2254(e)(2) in Shinn).
• There is no statutory basis for differentiating the diligence standard based on the substantive constitutional provision invoked.

In short, the same strict gatekeeping applies to both government‑misconduct and counsel‑ineffectiveness claims in the successive‑petition setting.

VI. The Court’s Legal Reasoning

A. The Appropriate Due Diligence Standard

Vasquez’s core argument was that the district court applied the wrong diligence standard. According to him, § 2244(b)(2)(B)(i) should ask what a reasonable petitioner could have discovered, not what a reasonable attorney would have known. He stressed this distinction because his new claim was itself an ineffective assistance claim—arguably made unfair if the gatekeeping standard presumes competent counsel in the first place.

The Fifth Circuit responds as follows:

1. The statutory text uses the passive voice and an objective standard: the factual predicate could not have been discovered “through the exercise of due diligence,” not “by this petitioner” or “by his lawyer.”
2. Johnson, Williams, and subsequent cases consistently interpret that phrase to mean an objective, reasonable‑attorney standard, at least for represented petitioners.
3. Nothing in AEDPA or prior precedent supports using one diligence standard for Brady/false‑testimony claims and a different one for Strickland claims.
4. Indeed, In re Coleman suggested that § 2244(b)(2)(B) will routinely conflict with, and thus bar, many ineffective assistance claims asserted in successive petitions.

Thus, when a petitioner was represented by counsel at trial and during the first federal habeas petition, as Vasquez indisputably was, the proper inquiry is:

Would a reasonable attorney, exercising due diligence at the time of the first federal habeas petition, have been on notice of—and able to discover—the factual predicate of the new claim?

B. Application: The Toxicology Report Was Always There

The court next applies this standard to Vasquez’s case. The key points:

• The Toxicology Report and trial testimony existed and were in counsel’s hands well before the first federal habeas petition was filed in 2006.
• At trial:
  • Dr. White testified that cocaine was detected in Miranda’s blood and that cocaine intoxication contributed to her death.
  • Dr. Backer testified that the initial testing “indicated the presence of cocaine,” and confirmatory analysis showed cocaine in the blood.
  • The Toxicology Report, however, recorded a “negative” result for “drugs of abuse,” while still including a later, quantified cocaine result.

This creates a facial conflict between:

• The “negative” preliminary screen (normally suggesting no drugs present), and
• The asserted high‑quantity cocaine finding and expert testimony based on it.

The panel characterizes this conflict as “readily discoverable” by any reasonably attentive attorney reviewing the record. Moreover, because Vasquez had always denied giving Miranda cocaine, a competent postconviction attorney reasonably should have scrutinized the toxicology evidence:

• A careful reading of the records would have revealed the negative screening result in tension with positive confirmatory findings.
• This, in turn, should have prompted further investigation—whether by expert consultation or otherwise—well before 2019.

Therefore:

“A reasonable attorney would have been put on notice of the conflict between trial testimony and the Toxicology Report before Vasquez’s prior federal habeas petition was filed.”

On that basis, the court holds that the factual predicate of Claim 6—trial counsel’s failure to expose or challenge the toxicology inconsistency—could have been discovered earlier with due diligence. AEDPA’s § 2244(b)(2)(B)(i) is therefore not satisfied.

C. No Equitable Exception to Statutory Due Diligence

Anticipating that conclusion, Vasquez argued in the alternative that an equitable exception to the diligence requirement was necessary for his case, especially given the severe stakes of a capital sentence and the later recantations by the State’s own experts.

The Fifth Circuit rejects this argument on both agency and separation‑of‑powers grounds:

1. Agency / attribution of counsel’s errors:
   • Under Shinn v. Ramirez, when counsel fails in postconviction proceedings, that failure is generally attributed to the prisoner because postconviction counsel is the prisoner’s agent.
   • Exceptions like Martinez v. Ryan are limited to the non‑statutory doctrine of procedural default, where the Sixth Amendment undergirds the analysis. Here, in contrast, we are dealing with a statute that Congress has adopted.
2. Separation of powers / statutory limits:
   • AEDPA’s § 2244(b)(2)(B) is a “constitutionally valid barrier to habeas relief.”
   • Citing Shinn, the court emphasizes that where Congress has erected such a barrier, courts “have no authority to amend” it by developing judicial exceptions.

In short, AEDPA’s due diligence requirement is mandatory. Courts may not carve out case‑by‑case exceptions, even if fairness concerns or attorney incompetence make a petitioner’s claim particularly sympathetic.

D. The Innocence Prong: Evidence of Intent Without Cocaine

Finally, although failure of the diligence prong is independently sufficient to affirm, the panel briefly addresses § 2244(b)(2)(B)(ii). Vasquez contended that, absent the cocaine evidence, no reasonable factfinder would have found that he acted with the requisite mens rea to commit capital murder.

The court disagrees, pointing to the “substantial additional evidence” of intent:

• Severity of head injuries:
  • Vasquez admitted that he hit Miranda.
  • She had numerous contusions to her face, head, and body.
  • Trial testimony described blows “hard enough to produce a fatal injury” and damage comparable to a high‑speed vehicular ejection.
• Evidence of sexual assault:
  • A State expert testified that Miranda’s perineal injuries were consistent with a severe sexual assault and restraint.
  • The expert described this as “one of the most severe sexual assaults” she had seen.
  • The State argued that the assault provided a motive to silence the child, reinforcing the inference of intentional or knowingly lethal conduct.

The panel notes that, regardless of the cocaine issue, it is “quite difficult to imagine” that an adult repeatedly inflicting forceful blows on a small child would not at least be aware that such conduct was reasonably certain to cause death. That is sufficient under Texas’s “knowingly” standard for murder.

Moreover, the jury actually saw the Toxicology Report, with the same negative‑screen / positive‑quantity tension that underlies the new claim. They thus already had the opportunity to discount the cocaine evidence if they found it inconsistent. The new expert’s critique does not clearly and convincingly establish that they would have acquitted if counsel had highlighted that inconsistency.

Accordingly, even “viewed in light of the evidence as a whole,” Vasquez’s new factual proffer does not meet the clear‑and‑convincing no‑reasonable‑factfinder standard of § 2244(b)(2)(B)(ii).

VII. Impact and Implications

A. Practical Consequences for Capital and Non‑Capital Habeas Litigation

Although unpublished and thus not binding precedent under Fifth Circuit Rule 47.5, Vasquez v. Guerrero offers a clear and rigorous application of existing AEDPA principles that will be highly persuasive in future cases. Its practical implications are significant:

1. First federal habeas counsel must be exhaustive with expert and record review.
   • Any anomalies, contradictions, or gaps in the trial record—particularly in critical scientific evidence—must be thoroughly investigated during the initial federal petition.
   • Later expert reinterpretations of existing data will almost always be deemed discoverable through earlier diligence and thus barred under § 2244(b)(2)(B)(i).
2. Successive ineffective assistance claims are particularly constrained.
   • Coleman and now Vasquez reinforce that § 2244(b)(2)(B) and Strickland sit uneasily together: proving both prior counsel’s deficiency and AEDPA‑level nondiscoverability is often impossible.
   • Practitioners must treat initial habeas litigation as the one realistic opportunity to press complex IAC theories based on the trial record and expert evidence.
3. No Martinez‑style lifeline in the AEDPA successive‑petition context.
   • Shinn and Vasquez together make clear that while Martinez can excuse some state procedural defaults, it does not soften AEDPA’s statutory bars to federal successive petitions.
   • In other words, a prisoner cannot argue that ineffective postconviction counsel supplies cause to evade § 2244(b)(2)(B)’s diligence requirement.
4. High bar for “new scientific evidence” in federal court.
   • Texas’s Article 11.073 allows state collateral attacks based on “new scientific evidence,” including later‑developed expert criticism of earlier methods or interpretations.
   • But in federal court, under AEDPA, the question is narrower: was the factual predicate (e.g., conflicting entries in a toxicology report) already discoverable? If so, later scientific critique does not satisfy § 2244(b)(2)(B)(i), even if it might qualify as “new science” under state law.

B. Reinforced Preference for Finality Over Error‑Correction

Vasquez vividly illustrates the post‑AEDPA shift from an error‑correction model to a strong finality model in federal habeas:

• The opinion acknowledges no space for equitable flexibility in the successive‑petition context, even where:
  • State trial experts have recanted or repudiated their prior testimony; and
  • The case involves the death penalty.
• The emphasis on what could have been done by a hypothetical reasonable attorney—as opposed to what actually was done by appointed counsel with finite time and resources—further demonstrates that Congress’s chosen baseline is an idealized level of diligence, not a realistic average.

For defendants and their lawyers, this underscores that:

Effective, comprehensive lawyering at the initial postconviction stage is not merely desirable; it is, under AEDPA, dispositive. Missed claims are often missed forever.

C. Doctrinal Clarity on the Scope of AEDPA’s Diligence Requirement

Doctrinally, Vasquez makes several points clear:

• The § 2244(b)(2)(B)(i) diligence requirement applies uniformly to all types of constitutional claims, including:
  • Brady/Giglio/Napue (prosecutorial misconduct / suppressed or false evidence), and
  • Strickland (ineffective assistance of counsel).
• Courts will not entertain doctrinal carve‑outs based on the nature of the underlying right (e.g., right to counsel vs. right to due process).
• Equitable doctrines such as Martinez and traditional habeas “miscarriage of justice” principles cannot override clear statutory text in AEDPA’s second‑or‑successive context.

VIII. Simplifying Key Legal Concepts

A. What Is a Successive Habeas Petition Under AEDPA?

A successive habeas petition is a second (or later) attempt to obtain federal habeas corpus relief after a prisoner’s first federal petition has been decided. AEDPA makes it extremely difficult to bring such a petition:

1. You must first get permission (“authorization”) from the court of appeals.
2. Even if you get that permission, the district court must independently confirm you meet very strict statutory conditions.

Those conditions are meant to protect finality and limit repetitive litigation of criminal convictions.

B. What Does “Due Diligence” Mean in This Context?

“Due diligence” in § 2244(b)(2)(B)(i) asks whether the factual basis of the new claim could not reasonably have been discovered earlier. It is:

• Objective: The court asks what a hypothetical “reasonable attorney” could have done, not what the actual lawyer did.
• Time‑bound: The relevant time is when the first federal habeas petition was filed; if the evidence was available in the record or could have been discovered with reasonable investigation then, later discovery does not satisfy AEDPA.

If the new claim is based on documents, transcripts, or exhibits that were already in the file, courts will usually find that the factual predicate could have been discovered with due diligence.

C. The “Innocence” Requirement of § 2244(b)(2)(B)(ii)

Even if due diligence is shown, § 2244(b)(2)(B)(ii) requires a separate and even more demanding showing:

• The new facts, if true and considered with all the other evidence, must show by clear and convincing evidence that no reasonable juror would have found the petitioner guilty.
• This is a much higher standard than simply showing “reasonable doubt” or that the new evidence “might have changed” the verdict.

In practice, this means:

If the State still has strong, independent evidence of guilt—even if some part of its case is undermined—the petitioner will often fail this standard.

D. Why Can’t Courts Create Equitable Exceptions Here?

Equity in law refers to the power of courts to do justice in individual cases, sometimes by creating judge‑made exceptions to general rules. However:

• With AEDPA, Congress has created detailed statutory rules governing when federal courts may consider successive habeas petitions.
• The Supreme Court in Shinn v. Ramirez has emphasized that courts cannot simply rewrite or relax those statutory commands based on equitable notions.
• Thus, unlike doctrines such as procedural default (which are largely judge‑made and can be modified by justice‑based exceptions like Martinez), AEDPA’s statutory bars must generally be applied as written.

IX. Conclusion

Vasquez v. Guerrero stands as a pointed reminder of the power and rigidity of AEDPA’s successive‑petition regime. The decision:

• Reaffirms that § 2244(b)(2)(B)(i)’s diligence requirement is assessed through the lens of a reasonable attorney, not a reasonable lay petitioner.
• Clarifies that this standard applies equally to claims of ineffective assistance of counsel as to claims of prosecutorial misconduct or false evidence.
• Underscores that no equitable exception exists to soften AEDPA’s statutory barriers, even where new expert analysis seriously questions key trial evidence and the case involves the death penalty.
• Illustrates that the separate clear‑and‑convincing innocence requirement of § 2244(b)(2)(B)(ii) is extremely difficult to satisfy when substantial independent evidence of guilt remains.

In a broader sense, Vasquez captures the post‑AEDPA landscape in which federal habeas review is tightly circumscribed, and the first round of habeas litigation is effectively the last meaningful opportunity for a prisoner to develop and present complex constitutional challenges. For lawyers, it is a cautionary tale about the absolute necessity of meticulous, expert‑informed investigation at the earliest postconviction stages. For courts and policymakers, it highlights the continuing tension between the goals of finality and the possibility of correcting deeply consequential errors discovered only years later.