DENVER (AP) — A man sentenced to death for killing a Texas couple camping in Oklahoma nearly 20 years ago won a chance on Monday to prove he should be spared the death penalty over questions about his lawyer's performance.

The 10th Circuit Court of Appeals in Denver ordered that a federal court in Oklahoma hold a hearing to review why Edward Leon Fields' lawyer did not present evidence of his brain damage to jurors during his sentencing trial in the 2003 killings of Charles and Shirley Chick of Hurst, Texas, in the Ouachita National Forest.

Fields' previous public defender, Julia O'Connell, did not have much experience with death penalty cases at the time and said in a written declaration as part of Fields' appeal that she was overwhelmed by the case.

During arguments before the 10th Circuit last month, one of Fields' current public defenders, Hunter Labovitz, said that O'Connell failed to call an expert who could have testified about how Fields' alleged brain damage impaired his judgement, reasoning and decision making when he killed the Chicks.

At the time, the appeals judges wondered whether that might have been a strategic decision to avoid undercutting her argument that Fields killed the couple after suffering a "manic flip" caused by Effexor, his anti-depressant medication. In their ruling, they said the district court should hold a hearing to weigh the evidence on why brain damage evidence was not introduced and, if it was mistakenly omitted, decide whether the potential lapse was significant enough to deprive Fields of a fair trial.

Fields' lawyers also claimed that O'Connell was ineffective for failing to present evidence of Fields' troubled childhood and not objecting to a Biblical reference in the government's closing arguments but the appeals court dismissed those claims.