AEDPA Deference and Strickland Review: Caballero v. Miller Clarifies Ineffective Assistance Standards

Introduction

The Second Circuit’s summary order in Caballero v. Miller (No. 24-2602-pr, decided April 2, 2025) resolves a habeas corpus petition filed under 28 U.S.C. § 2254. Petitioner Andrew Caballero challenged his New York state‐court conviction for murder on grounds of ineffective assistance of both trial and appellate counsel. After the Eastern District of New York granted relief, the State appealed. The Second Circuit reversed, emphasizing the high bar of Antiterrorism and Effective Death Penalty Act (“AEDPA”) deference and the two‐part Strickland standard for ineffective assistance of counsel.

Summary of the Judgment

The court held that:

The state court’s denial of Caballero’s ineffective‐assistance‐of‐trial‐counsel claim did not unreasonably apply Strickland v. Washington because Caballero failed to present evidence of what additional testimony or facts a more thorough investigation would have uncovered.
Caballero could not satisfy the prejudice prong of Strickland: there was no “reasonable probability” that, if counsel had investigated additional witnesses or alternative suspects, the jury’s verdict would have changed.
The claim of ineffective assistance of appellate counsel likewise failed, both because New York law channels such claims into collateral proceedings and because Caballero could not show a reasonable probability of appellate success.
The district court’s grant of habeas relief under § 2254 was reversed, and the petition was denied.

Analysis

1. Precedents Cited

Strickland v. Washington, 466 U.S. 668 (1984): established the two‐prong test for ineffective assistance—deficient performance and prejudice.
AEDPA § 2254(d): requires federal habeas relief only if the state court decision was “contrary to, or involved an unreasonable application of, clearly established Federal law.”
Lindstadt v. Keane, 239 F.3d 191 (2d Cir. 2001): example of clear prejudice when counsel fails to interview witness whose testimony would have undercut prosecution’s key witness.
Schulz v. Marshal, 345 F. App’x 627 (2d Cir. 2009): counsel’s failure to interview a potential eyewitness who later identified someone else, demonstrating prejudice.
Pierotti v. Walsh, 834 F.3d 171 (2d Cir. 2016): New York rule that claims relying on evidence outside the trial record must be brought in collateral proceedings.
Rosario materials (People v. Rosario, 9 N.Y.2d 286 (1961)): state‐law requirement to disclose witness statements to the defense.

2. Legal Reasoning

The court’s reasoning rests on two intertwined deferential standards:

AEDPA Deference: Under 28 U.S.C. § 2254(d), a federal court may grant habeas relief only if the state court ruling on an issue was not only mistaken but “unreasonable.” This imposes “doubly deferential” review when combined with Strickland.
Strickland Standard: To prevail on ineffective assistance of counsel, a petitioner must show (a) counsel’s performance was objectively unreasonable and (b) there is a reasonable probability that, but for the errors, the outcome would have differed.

Here, Caballero argued that trial counsel Michael DiDio should have investigated Rosario-disclosed witnesses and pursued Michael Lugo as an alternative suspect. He contended that the absence of any forensic evidence and counsel’s purported confusion about the crime scene compounded prejudice. The Second Circuit held:

Performance: While a reasonable attorney might have pursued additional leads, the real question is whether the state court unreasonably concluded no prejudice.
Prejudice: Caballero provided no affidavits, witness affidavits, or hearing testimony establishing what new evidence those investigations would have produced. Unlike Lindstadt or Schulz, there was no post‐trial declaration showing an eyewitness would have changed testimony.
Without concrete evidence of what further investigation would have revealed, Caballero could not satisfy the “reasonable probability” standard. The state court’s contrary finding was a permissible application of Strickland under AEDPA.
On appellate counsel, New York law requires collateral, not direct, review of claims that rely on evidence outside the record. Even if that were not so, Caballero could not demonstrate a likelihood of success on the merits of the underlying claim.

3. Impact

This decision reinforces several key principles in future federal habeas and state collateral proceedings:

Petitioners bear the burden of showing Strickland prejudice by identifying precisely what additional evidence more thorough counsel would have uncovered and how it would have changed the outcome.
AEDPA’s “unreasonable application” standard demands more than a federal judge’s disagreement with a state court—it requires proof that the state court’s conclusion was beyond fair debate.
New York defendants must bring claims dependent on evidence outside the trial record in § 440 collateral proceedings, not on direct appeal.
The decision curbs attempts to secure habeas relief based solely on generalized assertions of deficient investigation without concrete witness statements or affidavits to substantiate prejudice.

Complex Concepts Simplified

AEDPA Deference: Federal habeas courts must give significant respect to state‐court decisions. A petitioner wins only if the state court’s ruling is more than wrong—it must be unreasonable.
Strickland Two‐Prong Test: (1) Did counsel perform unreasonably under professional norms? (2) If so, is there a reasonable chance the outcome would have been different?
“Reasonable Probability” of a Different Outcome: Not certainty—the test asks whether the error undermines confidence in the result.
Rosario Materials: New York’s rule that prior statements of witnesses must be turned over to the defense to allow effective cross‐examination.
Collateral vs. Direct Appeal: Claims requiring evidence beyond what was in the trial transcripts must be raised in a separate motion after conviction (a § 440 motion in New York), not on the initial appeal.

Conclusion

Caballero v. Miller sharpens the interplay between Strickland’s ineffective assistance test and AEDPA’s heightened deference standard. It underscores that habeas petitioners must do more than allege counsel failed to pursue leads—they must supply evidence of what those leads would have yielded and how they would have altered the verdict. The ruling also reaffirms procedural requirements in New York for bringing claims dependent on evidence outside the trial record. Taken together, this decision will guide defense counsel, state courts, and federal habeas courts in assessing the adequacy of counsel’s investigation and the feasibility of collateral relief under § 2254.