Caballero v. Miller: Setting the Prejudice Threshold for Ineffective-Assistance Claims Under AEDPA

Introduction

Caballero v. Miller, 24-2602-pr (2d Cir. Apr. 2, 2025), addresses the intersection of the Antiterrorism and Effective Death Penalty Act (AEDPA) and the Supreme Court’s two-pronged Strickland standard for ineffective assistance of counsel. Petitioner Andrew Caballero challenged his New York murder conviction via a federal habeas petition under 28 U.S.C. § 2254, claiming that his trial lawyer (DiDio) and his direct-appeal lawyer (Muscatello) provided constitutionally deficient assistance. The Eastern District of New York granted relief, but the Second Circuit reversed. In doing so, the Court reaffirmed that under AEDPA’s deferential review, a habeas petitioner bears the burden of showing not only deficient performance, but also a “substantial likelihood” of prejudice—something Caballero failed to do because he could not demonstrate what additional evidence a more thorough investigation would have produced.

Key issues:

Did trial counsel’s failure to investigate certain witnesses or an alternative suspect constitute objectively unreasonable performance?
Could that failure have prejudiced the outcome of a state‐court jury trial?
Was appellate counsel ineffective for not raising that claim on direct appeal?
How does AEDPA’s “unreasonable application” standard shape the federal court’s review?

Parties:

Petitioner-Appellee: Andrew Caballero, convicted of murder in New York state court.
Respondent-Appellant: Christopher Miller, Warden/Superintendent of Comstock Correctional Facility.

Summary of the Judgment

The Second Circuit, in a summary order, reversed the district court’s grant of habeas relief. Although it assumed that trial counsel may have performed deficiently by not investigating several Rosario‐disclosed witnesses and an alternative suspect (Michael Lugo), the Court held that Petitioner failed to satisfy Strickland’s prejudice prong under AEDPA’s doubly deferential standards. Without any evidentiary showing of what additional testimony the uncontacted witnesses would have provided, Caballero could not show a reasonable probability of a different trial outcome. Likewise, appellate counsel’s failure to raise that claim on direct appeal was not prejudicial because the underlying prejudice had not been established. The Court therefore reversed the grant of the writ.

Analysis

Precedents Cited

Strickland v. Washington, 466 U.S. 668 (1984) – Established the two-pronged test for ineffective assistance: (1) deficient performance and (2) prejudice “so serious as to deprive a defendant of a fair trial.”
28 U.S.C. § 2254(d) / AEDPA – Requires that federal habeas relief may issue only if the state‐court decision “resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established Federal law.”
Harrington v. Richter, 562 U.S. 86 (2011) – Emphasized the double deference when Strickland and AEDPA both apply: federal courts must ask whether the state court’s decision was “objectively unreasonable.”
Lindstadt v. Keane, 239 F.3d 191 (2d Cir. 2001) – Demonstrated a clear prejudice showing where uncalled witnesses could have corroborated petitioner’s claims and undercut the prosecution’s chief witness.
Schulz v. Marshal, 345 F. App’x 627 (2d Cir. 2009) – Held prejudice established where an uninvestigated eyewitness later identified a different perpetrator.

Legal Reasoning

1. Deficient Performance: The Court assumed, without deciding, that counsel’s investigation fell below an objective standard by not contacting Rosario‐disclosed witnesses (e.g., Peralta, Moses, Newmark) or probing Lugo as an alternative suspect. Nor did counsel map out the apartment’s layout before cross‐examination.

2. Prejudice Under Strickland: A petitioner must show a reasonable probability that, but for counsel’s errors, the verdict would have been different. Under AEDPA, this inquiry is subject to an additional layer of deference; a federal court may grant relief only if the state court’s prejudice determination was unreasonable.

3. Failure to Demonstrate Prejudice:

No witness testimony or affidavits revealed what helpful evidence a proper investigation would have uncovered.
Many Rosario statements were double hearsay or speculative (e.g., “everyone knows Lugo did it,” “I heard from Amanda”).
Key witnesses (Pabon, Cavalieri) still placed Caballero with the victim shortly before and after the crime—no clear evidence that further investigation would have yielded exculpatory facts.
Thus, the state court reasonably concluded that Petitioner failed to “affirmatively prove prejudice.”

4. Appellate Counsel: Under New York law and Strickland, appellate counsel need not raise claims that require evidence beyond the trial record; ineffective assistance claims based on extra-record facts belong in collateral proceedings. Even if counsel had erred by omitting the claim, Petitioner could not show a reasonable probability of success on appeal, since prejudice was lacking.

Impact

Caballero v. Miller clarifies two important points:

Prejudice Requirement: Under AEDPA, habeas petitioners relying on a failure-to-investigate theory cannot meet Strickland’s prejudice prong merely by pointing to deficient performance. They must show what additional reliable evidence an investigation would have uncovered and that it would likely have altered the verdict.
Appellate-Counsel Claims: Challenges to direct-appeal counsel for failing to raise a claim dependent on extra-record evidence are likely to fail unless the petitioner can prove both deficient performance and resulting prejudice—especially when state law requires collateral proceedings for such claims.

Future habeas petitioners will face stringent demands to proffer affidavits or testimony establishing what witnesses would have said and how that testimony would have undermined the prosecution’s case.

Complex Concepts Simplified

AEDPA Deference: Once a state court has ruled on a federal claim, a federal habeas court may grant relief only if that ruling was not just wrong, but “objectively unreasonable” under Supreme Court precedent.
Strickland Test: A two-part inquiry into counsel’s performance: (1) Was performance objectively unreasonable? (2) Did the lawyer’s errors prejudice the outcome?
Rosario Material: In New York, prosecutors must disclose prior statements by their witnesses so defense counsel can use them for cross-examination.
Summary Order: A decision by the Second Circuit that does not establish binding precedent but applies existing law to the facts of a case.

Conclusion

Caballero v. Miller reinforces the high bar that AEDPA and Strickland together set for federal habeas relief. Even assuming trial counsel performed deficiently by failing to investigate potential witnesses and alternative suspects, a habeas petitioner must affirmatively demonstrate a substantial likelihood that a proper investigation would have yielded evidence changing the verdict. Without it, there can be no constitutional prejudice, and appellate counsel cannot be faulted for failing to raise a claim doomed by the absence of such evidence. This decision safeguards the finality of state convictions against speculative or unsupported allegations of ineffective assistance.