Mason v. Mitchell:

Maurice Mason was sentenced to death for the rape and murder of Robin Dennis in 1994. After exhausting his appeals, he filed a habeas corpus petition alleging, among other things, ineffective assistance of counsel. In 2003, the U.S. Court of Appeals for the Sixth Circuit remanded his case to the district court ordering an evidentiary hearing on his claim of ineffective assistance of counsel during his sentencing phase due to his counsel's alleged failure to conduct a reasonable investigation into Mason's family background. The district court held the required hearing, concluded Mason's counsel was not constitutionally ineffective, and denied Mason's petition.

On Friday, a divided panel of the U.S. Court of Appeals for the Sixth Circuit reversed the district court and granted Mason's habeas petition in an opinion by Judge Karen Moore, joined by Judge Eric Clay. According to the majority:

Although Mason's counsel reviewed records provided by the state that contained some references to violence and drug use in the Mason family home during Mason's childhood, Mason's counsel failed to investigate Mason's background and essentially conducted no interviews of any of Mason's family members prior to settling upon a plan for the sentencing phase that was limited to appeals for mercy and claims of residual doubt. We hold that trial counsel provided ineffective assistance by failing to interview Mason's family members and investigate the obvious red flags contained in state records suggesting that Mason's childhood was pervaded by violence and exposure to drugs in the home from an early age.
Judge Danny Boggs dissented.
After we remanded to give the condemned exactly what he asked for, an evidentiary hearing before a federal district judge, the learned trial judge carefully reviewed the evidence presented and correctly applied the relevant federal law under AEDPA and Strickland v. Washington. Today our court continues a distressing trend of finely parsing defense counsel judgments, based on the most charitable (to the condemned) or malevolent (to the defense counsel) view of facts and holds that counsel was constitutionally ineffective. I emphasize constitutionally because in a common-sense way, counsel was of course ineffective -- his client was sentenced to death. However, that is not the standard that we are to apply, and I therefore dissent.
Judge Boggs opinion concludes:
This opinion sets an almost impossibly high bar for defense counsel in capital cases. Defense counsel is now required "to locate and interview the client's family members . . . and virtually everyone else who knew the client and his family, including neighbors, teachers, clergy, case workers, doctors, correctional, probation or parole officers, and others" . . . ; he must interview them long enough so that those interviews can be characterized as "extensive" and "in-depth"; every conceivable family member must be contacted, no matter that defense counsel has spoken with the defendant, his wife, mother, father, brother, sister, aunt, and cousin (along with several non-family members); and he must do all this even if he reasonably believes (based on the trial court's rulings and his own reasonable interpretation of state law) that the introduction of any evidence regarding the defendant's family background could open the door to truly disastrous rebuttal evidence by the prosecution. Nothing in Strickland or its progeny requires defense counsel to go to such extreme lengths in order to meet the (relatively low) threshold of "reasonably effective assistance."