CHEYENNE, Wyo. (AP) — Lawyers for Wyoming's lone death row inmate have filed a massive court brief asking a federal judge to overturn his death sentence.

Inmate Dale Wayne Eaton is challenging the constitutionality of the death sentence he received in 2004 for rape and murder of 18-year-old Lisa Marie Kimmell of Billings, Mont.

The Wyoming Supreme Court already has upheld the 68-year-old's conviction but the federal court has put the execution on hold.

Eaton's current lawyers don't dispute that he killed Kimmell in 1988. But they claim he didn't get an adequate defense from public defenders.

Eaton's lawyers filed the 300-page brief in federal court last week. Echoing testimony at a hearing this summer, it claims his defense team didn't present adequate mitigating evidence of Eaton's tortured personal history and mental health issues.