A mental health expert has found Louisiana serial killings suspect Derrick Todd Lee (search) to be mentally retarded, a lawyer said Tuesday in a new twist that could be used to try to spare Lee a possible death penalty.

Public defender Mike Mitchell (search) made the announcement as jury selection continued for Lee's first-degree murder trial in the beating and stabbing death of 22-year-old Charlotte Murray Pace.

It is the first trial Lee has faced that carries a possible death penalty, but a Supreme Court ruling bars the execution of mentally retarded criminals.

Prosecutors say DNA evidence (search) links Lee to the slaying of Pace — who was killed May 31, 2002 — and six other women in southern Louisiana between April 1998 and March 2003. He has been convicted of one of the killings and was sentenced to life in prison last month.

Mitchell said he received a single-line e-mail from the mental health expert a day earlier but not a formal report, and he said he was trying to obtain more information.

Prosecutor John Sinquefield said he was surprised by the information because he had requested last year to be informed by defense lawyers if they planned to argue that Lee was mentally retarded.

"After 13 months of requesting that notice, this is the first time I receive any notification," Sinquefield told State District Judge Richard Anderson.

Sinquefield said prosecutors are entitled to a separate and independent evaluation of Lee by a psychiatrist, but he said the court has time to handle the matter without interfering with the trial because any penalty phase if Lee is convicted would still be weeks away.

The judge urged defense attorneys to "get the ball rolling" and file a notice of intention to present the matter.

Jury selection has stretched into its second week, with nearly 30 potential jurors dismissed from a pool of more than 400. Ten potential jurors have made it through questioning, but they could be removed later by lawyers on either side as they work to assemble a 12-member jury with four alternates.