OKLAHOMA CITY -- A longtime lawyer for Oklahoma's prison system said Thursday that he felt pressured by the governor's and attorney general's offices to make sure executions last spring happened on schedule, even though the state didn't have the drugs yet to carry them out.

Oklahoma adopted a new protocol before executing Clayton Lockett last April. After the execution team administered the sedative midazolam and two other drugs intended to stop his breathing and his heart, Lockett mumbled and struggled on a gurney before dying.

Lockett's 43-minute execution prompted the state to impose a moratorium, which is set to end Jan. 15. A federal judge this week is considering whether death row inmates have a valid complaint that the state's Corrections Department is essentially experimenting on them by using untested drugs or drug combinations during executions.

Lockett's execution was initially scheduled for March 20, but three days before then the state attorney general's office said Oklahoma didn't have sufficient drugs on hand and couldn't meet the criteria to switch to electrocution or a firing squad.

In subsequent weeks, the state changed protocols to let it use midazolam, a sedative commonly used before surgery. In a January execution, an Ohio inmate made gasp-like sounds for several minutes before dying. The drug also was used in a lengthy Arizona execution in July.

In testimony Thursday before U.S. District Judge Stephen Friot, Corrections Department lawyer Michael Oakley said he felt pressured "to get it done."

Lockett and Charles Warner's execution were each set for April 29, but Gov. Mary Fallin issued a stay after the trouble during Lockett's death. Warner is schedule to die Jan. 15, then three more executions are scheduled through March 5.

Prison officials have said guidelines adopted after Lockett's death will ensure future executions go smoothly.