Attorneys for 33 death row inmates have asked a judge to declare Tennessee's preferred method of executing prisoners unconstitutional.

The trial that began July 7 in Davidson County Chancery Court concluded Wednesday.

During closing arguments, inmates' attorneys discussed technical aspects of the procedure, including the role of compounding pharmacists in producing the lethal injection drug pentobarbital.

About two years ago, the state moved from a three-drug lethal injection method to a one-drug method using pentobarbital. However, plaintiffs' attorneys say the compounded form of the drug is likely to cause a condemned inmate to suffer extreme pain and can cause a lingering death.

Although Tennessee has yet to carry out an execution using compounded pentobarbital, the state's attorney said Texas, Ohio and Georgia have had more than 30 successful and painless executions with the drug.