Rompilla (plaintiff) was convicted of murder. At sentencing, the prosecution introduced evidence of Rompilla’s prior felony convictions as aggravating factors to justify imposing the death penalty. The defense presented testimony from family members as mitigating evidence. Rompilla’s lawyers had interviewed Rompilla and his family members to search for mitigating factors. The jury sentenced Rompilla to death. The state supreme court affirmed the conviction and death sentence. Rompilla obtained new lawyers and filed an ineffective assistance of counsel claim, arguing that his trial lawyers failed to present several mitigating factors. The court found that Rompilla’s trial lawyers had done reasonable research regarding mitigating factors. Rompilla petitioned for a writ of habeas corpus in federal district court. The federal district court held that the state supreme court had misapplied the standard for ineffective assistance of counsel as set out in Strickland v. Washington, 466 U.S. 668 (1984). Under Strickland, ineffective assistance is deficient performance by counsel that results in prejudice. The federal court granted Rompilla relief for ineffective assistance of counsel. The United States Court of Appeals for the Third Circuit reversed and held that the trial lawyers used reasonable efforts to uncover mitigating factors. The United States Supreme Court granted certiorari.