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ST. LOUIS (AP) – A Missouri man convicted of killing a woman and her two children in 1998 has asked the U.. Supreme Court to halt his execution.

Mark Christeson is scheduled for lethal injection Tuesday evening. If carried out, it will be Missouri’s first execution since May.

The main issue raised in Christeson’s appeal Monday is that his trial lawyers were inept, noting they missed a 2005 deadline for a federal appeal, which is a standard procedure in death penalty cases.

Christeson was 18 when he and a 17-year-old cousin attacked Susan Brouk at her rural home in Vichy, then killed Brouk, her 12-year-old daughter and her 9-year-old son.

The cousins were caught after fleeing to California.

Christeson’s cousin testified against him and was sentenced to life in prison without parole.