Francis Hernandez v. Kevin Chappell, 878 F.3d 843

In 1981 Francis Hernandez was convicted by a jury of two counts of first‑degree murder (with rape/sodomy special circumstances), two counts of rape, and two counts of forcible sodomy; the jury imposed death for the murder counts.
Trial counsel presented a diminished‑capacity defense based solely on voluntary intoxication and did not investigate or present evidence of lifelong mental impairment, neuropsychological injury, or severe childhood abuse.
Post‑conviction experts (on habeas) developed extensive evidence of genetic predisposition to severe mental illness, in utero injury, repeated childhood head trauma, dissociation, organic brain damage, and severe abuse by adoptive parents—evidence the trial jury never heard.
The district court granted habeas relief as to sentencing (vacating the death penalty) but denied guilt‑phase relief, finding counsel deficient but concluding no prejudice from the omission of the mental‑impairment diminished‑capacity defense.
The Ninth Circuit majority held counsel’s failure to investigate the available diminished‑capacity defense was constitutionally deficient and that the omitted mental‑impairment evidence created a reasonable probability at least one juror would have had reasonable doubt as to first‑degree murder; it reversed the denial of guilt‑phase relief and ordered a new trial unless the state reprosecutes.

Issue	Plaintiff's Argument (Hernandez)	Defendant's Argument (State)	Held
Whether counsel’s failure to investigate/present a diminished‑capacity defense based on mental impairment constituted deficient performance under Strickland	Counsel admitted he did not know the defense was available and would have pursued it; failure to research law and facts was unreasonable	Any failure was strategic or reasonable because trial experts were inconclusive and intoxication theory sufficed	Held: counsel’s ignorance of the law and failure to investigate was objectively unreasonable and therefore deficient performance
Whether the deficient performance prejudiced the outcome of the guilt phase (reasonable probability of different result)	Extensive expert evidence of genetic predisposition, brain injury, dissociation, and trauma could have negated specific intent/malice and undermined first‑degree murder verdicts	The confession’s detail, similar crimes close in time, and physical evidence of premeditation made a different outcome unlikely; rebuttal experts could have countered habeas experts	Held: omitted mental‑impairment evidence likely would have created reasonable doubt in at least one juror as to specific intent; prejudice found and conviction vacated (guilt‑phase)

Strickland v. Washington, 466 U.S. 668 (ineffective assistance standard: deficient performance and prejudice)
Harrington v. Richter, 562 U.S. 86 (no post‑hoc rationalization of counsel’s reasons)
Hinton v. Alabama, 134 S. Ct. 1081 (attorney’s ignorance of fundamental law and failure to investigate can be Strickland error)
People v. Saille, 54 Cal. 3d 1103 (California recognition of diminished capacity for intoxication or mental illness)
People v. McDowell, 69 Cal. 2d 737 (diminished capacity based on mental abnormality; counsel deficient for failing to present such a defense)
Daniels v. Woodford, 428 F.3d 1181 (9th Cir.) (prejudice where counsel failed to present substantial mental‑impairment evidence)