William Morva watches as prospective jury members are interviewed to serve in his attempted robbery trial in Montgomery County Circuit Court in Christiansburg, Va.,in 2007. (Matt Gentry/AP)

Several Democratic members of the Virginia General Assembly have joined thousands of petitioners in asking Gov. Terry McAuliffe (D) to block the execution of convicted murderer William C. Morva, scheduled for Thursday.

Morva, 35, faces the death penalty for shooting to death a guard and a sheriff’s deputy while escaping from jail in 2006. Supporters say the jury that sentenced him was not made aware of the severity of his mental illness.

“The system failed Mr. Morva,” Del. Mark H. Levine (D-Alexandria) wrote on Monday. “I do not believe he should die because of a lack of due process.”

Levine was adding his name to a group of legislators who wrote McAuliffe on Friday seeking clemency for Morva. The seven delegates and five state senators, all Democrats, said the case intersects with a rising effort by the General Assembly to take steps to “address the overlapping areas of public safety, criminal justice and mental health.”

That letter asks McAuliffe to commute Morva’s death sentence to a term of life without parole. It was signed by Dels. Jennifer B. Boysko (Fairfax), Patrick A. Hope (Arlington), Sam Rasoul (Roanoke), Marcus B. Simon (Fairfax), Charniele Herring (Alexandria), Alfonso Lopez (Arlington) and Eileen Filler-Corn (Fairfax), as well as Sens. Adam P. Ebbin (Alexandria), Barbara A. Favola (Arlington), Lionell Spruill Sr. (Northern Chesapeake), Mamie E. Locke (Hampton) and Scott Surovell (Eastern Fairfax).

Morva’s lawyer argues that he was suffering from severe delusional disorder while being held in jail in the Blacksburg area awaiting trial for several botched robberies and burglaries. Believing that he was going to die, Morva tried to escape and killed the deputy and guard.

During sentencing, supporters say, jurors were told incorrectly that Morva was not delusional. His pending execution, set for 9 p.m. Thursday, highlights a growing national movement to eliminate capital punishment for people with severe mental illness.

Morva ran out of appeals when the U.S. Supreme Court declined to take up his case in February, leaving the governor as his last hope. McAuliffe has said he is studying the case, and a spokesman said Monday that the governor would make a statement when the review is complete.