A judge has struck down Montana’s lethal injection procedure as a violation of the state constitution’s protections against cruel and unusual punishment, effectively suspending executions in the state, officials said Friday.

State District Court Judge Jeffrey Sherlock did not question the constitutionality of the death penalty in Montana, which has two inmates on death row and has executed three since the death penalty was reinstated in 1976.

But he ruled, in a written decision handed down on Thursday, that the state’s three-drug execution procedure differs from a two-drug protocol spelled out in law, which he said “increases the likelihood of confusion and error in the process.”

Sherlock also faulted a practice in Montana that allows a prison warden with no medical training or execution experience to determine whether a prisoner is unconscious before a fatal drug is administered.

He also found that the prison official setting up the execution process is not required to have experience with the intravenous procedure.

Sherlock said those concerns and the disparity between the protocol in state law and the one practiced by the Department of Corrections created “a substantial risk of serious harm.” He also said the problems could easily be remedied by the legislature and the state corrections department.

Montana Assistant Attorney General C. Mark Fowler said in a statement that the state was studying the ruling “and determining what options were available to modify the protocol.” He added that no executions were scheduled.

Sixteen states and the District of Columbia have no death penalty, and there has been a gradual trend away from capital punishment in the country, with the number of executions falling slightly in recent years.

The decision stemmed from a lawsuit brought in 2008 by the Montana American Civil Liberties Union and attorneys for death row inmate Ronald Allen Smith, a Canadian convicted of shooting and killing two people in Montana in 1982.

Smith’s execution was stayed last year pending the outcome of the lawsuit. Smith has also petitioned Montana Governor Brian Schweitzer for clemency.

Ron Waterman, an attorney for Smith, said in a statement that he was pleased the court recognized that insufficiencies in the state’s lethal injection protocol “create a situation where execution could inflict pain and suffering.”

Convicted killer William Gollehon, the only other prisoner on death row in Montana, was later added as a plaintiff in the case.