Attorneys for a man convicted of fatally shooting his 9- and 6-year-old daughters in Dallas nearly 17 years ago as their mother listened on the telephone say he's mentally incompetent to be executed this week.

Lawyers for 62-year-old John David Battaglia have asked a federal appeals court and the U.S. Supreme Court to block his lethal injection scheduled for Thursday evening in Texas.

The former accountant's mental competency long has been an issue in his case. Evidence shows Battaglia has used a prison library to research capital cases that focused on competency and a state judge who ruled him competent described him as cunning and smart enough to figure out how to avoid his punishment.

Battaglia's daughters, Faith and Liberty, were shot and killed in an apparent revenge attack against their mother.