Wood, who was sentenced to death in 1992 for the murders of 6 young women, was given a stay of execution two years ago so his lawyers could prepare an appeal.
A hearing Tuesday on Wood's mental competency is the result of a 2002 U.S. Supreme Court ruling that executing a mentally retarded person constitutes cruel and unjust punishment in violation of the U.S. Constitution, the El Paso (Texas) Times reported.
The Texas Health and Safety Code states mental retardation originates during the development period so Wood's lawyers must establish that his deficiency existed before the age of 18.
To do that, they have requested his school records and the mental health records of his biological mother.
The mother of one of Wood's victims, who planned to attend Tuesday's hearing, said she does not believe Wood is mentally retarded.
"He buried the victims, which tells me that he knew what he was doing," said Marcia Fulton, the mother of victim Desiree Wheatley.