OKLAHOMA CITY — One week before a man's scheduled execution for killing a baby, the head of Oklahoma's prison system said he's confident in his staff's ability to carry out the first lethal injection in the state since one went awry in April.

Department of Corrections Director Robert Patton told the Board of Corrections on Thursday that the prison staff at the Oklahoma State Penitentiary in McAlester has worked "very hard" to prepare for the execution and three others planned soon.

"The staff at the Oklahoma Department of Corrections has trained very, very hard, and I'm very confident in their abilities," said Patton, who declined further comment because the new execution protocols still are being challenged in court.

Charles Warner is scheduled to die next Thursday for the 1997 killing of his roommate's 11-month-old daughter. Warner was scheduled to be executed the same night as Clayton Lockett, whose lethal injection went awry when an intravenous line failed. Patton tried to halt Lockett's execution after he writhed on the gurney, moaned and clenched his teeth, but Lockett died anyway 43 minutes after the execution began.

After a state investigation, prison officials made several changes, including new medical equipment for finding veins, backup execution drugs, more training for staff and a renovated execution chamber with new audio and video equipment.

Warner and three other death row inmates scheduled to die over the next few months have sued to halt their executions, claiming the use of the sedative midazolam as the first in a three-drug combination presents a risk of unconstitutional pain and suffering. A federal judge rejected those arguments last month, but the inmates are appealing to the 10th U.S. Circuit Court of Appeals in Colorado.

In a brief filed with the court this week, attorneys for the state of Oklahoma said its citizens have a compelling interest in seeing Warner and the other men executed for their crimes.

"The citizens should not see their criminal justice system derailed and subverted by criminal defendants who have completely exhausted the entire range of appeals and processes required by the U.S. and Oklahoma Constitutions due to baseless speculation of theoretical harms," state attorneys wrote.

The inmates claim midazolam, which was used for the first time in Oklahoma during Lockett's execution, won't properly anesthetize them before the second and third drugs are administered. But Florida has used the same three-drug combination in 11 executions without problems, and is scheduled to use it again on the same day as Warner's execution.

Oklahoma prison officials have acknowledged the sedative is not their first choice, but that other more effective drugs are not available because manufacturers refuse to provide them for use in executions.

Following Warner, Richard Eugene Glossip's execution is set for Jan. 29. John Marion Grant is scheduled to die on Feb. 19, and Benjamin Robert Cole's execution is planned for March 5.