Criminal defendants are guaranteed effective assistance of counsel, including adequate pretrial investigation, because they require the skill and knowledge of an individual trained in the adversarial process to identify the most important witnesses and evidence in order to present the most effective defense. Norman Gaines, following a jury trial, was convicted of capital felony, two counts of murder and conspiracy to commit murder in connection with the shooting death of Gary Louis-Jeune and Marsha Larose. He was sentenced to life imprisonment without the possibility of release. Gaines filed an amended petition for a writ of habeas corpus alleging ineffective assistance by trial counsel, Alexander Schwartz, including by failing to adequately investigate and discover two alibi witnesses. After hearing testimony, including from Madeline Rivera, whose name Gaines had given to Schwartz before trial, and Luz Davila, that Gaines was assisting Rivera move on the night in question, the habeas court granted the petition and ordered a new trial. The Appellate Court affirmed the judgment. The state appealed. The majority of the Supreme Court affirmed the Appellate Court’s judgment. The habeas court properly determined that Schwartz’s failure to investigate Rivera and, therefore, his failure to locate and interview Davila, did not fulfill his duty to undertake a reasonable investigation under the circumstances. Customary deference to trial strategy did not apply. Schwartz did not claim that he made an informed decision not to investigate Rivera in conjunction with a reasonable trial strategy. He could not explain why neither he nor his investigator had attempted to contact her. Schwartz acknowledged that, had he known the substance of their testimony, he would have called them to testify and believed it would have changed the verdict returned. Although merely mentioning an individual is not necessarily sufficient to trigger counsel’s duty to investigate in all cases; here, it was unreasonable for Schwartz not to investigate Rivera after Gaines identified her. Rivera was one of two individuals Gaines discussed as people he knew in Bridgeport. The then 16 year old had been residing in Bridgeport for only a few months. Rivera also was the sister and neighbor of a key state’s witness. The habeas court properly found that the alibi testimony likely would have created reasonable doubt as to Gaines’ guilt and led to a different verdict. Justice Zarella dissented.