Sears v. Upton, 561 U.S. 945 (Jun. 29, 2010)

After the defendant was sentenced to death in state court, a state post-conviction court found that the defendant’s lawyer conducted a constitutionally inadequate penalty phase investigation that failed to uncover evidence of the defendant’s significant mental and psychological impairments. However, the state court found itself unable to assess whether counsel’s conduct prejudiced the defendant; because counsel presented some mitigating evidence, the state court concluded that it could not speculate as to the effect of the new evidence. It thus denied the defendant’s claim of ineffective assistance. The United State Supreme Court held that although the state court articulated the correct prejudice standard (whether there was a reasonable likelihood that the outcome of the trial would have been different if counsel had done more investigation), it failed to properly apply that standard. First, the state court put undue reliance on the assumed reasonableness of counsel’s mitigation theory, given that counsel conducted a constitutionally unreasonable mitigation investigation and that the defendant still might have been prejudiced by counsel’s failures even if his theory was reasonable. More fundamentally, the Court continued, in assessing prejudice, the state court failed to consider the totality of mitigation evidence (both that adduced at trial and the newly uncovered evidence). The prejudice inquiry, the Court explained, requires the state court to speculate as to the effect of the new evidence. A proper prejudice inquiry, it explained, requires the court to consider the newly discovered evidence along with that introduced at trial and assess whether there is a significant probability that the defendant would have received a different sentence after a constitutionally sufficient mitigation investigation.