The state Supreme Court ruled today that convicted child killer Damien Echols is not entitled to a hearing to determine whether he was mentally competent during his trial. The justices ruled unanimously that Echols did not exercise due diligence in pursuing the point since his trial nearly a decade ago. Justice Donald Corbin wrote in the opinion that the defense team was aware of Echols` history of mental treatments at the time of trial. The opinion said Echols` claim that his lawyers were unaware of his mental state is unfounded. The court also rejected Echols` argument that authorities withheld information about another possible suspect in the killings. Had it ruled Echols` trial lawyers were incompetent, the high court could have thrown out the conviction and ordered the new trial. Second-graders Steven Branch, Michael Moore and Christopher Byers disappeared May fifth, 1993, while riding bicycles in their quiet, tree-lined neighborhood in West Memphis. Their bodies were found the next day in a watery ditch near their homes. Echols, Jason Baldwin and Jessie Misskelley, all teenagers at the time, were convicted in the murders. Echols was the only one sentenced to death. Baldwin is serving life without parole. Misskelley was sentenced to life in prison plus 40 years.