CONCORD, N.H . — An attorney for New Hampshire’s only death row inmate is challenging the constitutionality of the state’s death penalty law.

In a recently filed motion, a lawyer for Michael Addison argued that the two methods of execution allowed by New Hampshire – lethal injection and hanging – violate the state and federal constitution, including the Eighth Amendment’s ban on cruel and unusual punishment.

Addison was sentenced to death for the 2006 killing of Manchester police officer Michael Briggs. The state Supreme Court upheld his sentence in April.

David Rothstein, Addison’s attorney, said he also plans to file an appeal of the case with the U.S. Supreme Court within the next month.

New Hampshire’s last execution was in 1939, and lethal injection was added as an execution method in 1986. The state has no designated facility for carrying out executions. Department of Corrections Commissioner William Wrenn has said the state may use a prison gymnasium to carry out Addison’s execution rather than construct a costly new facility.

In the motion, first reported by New Hampshire Public Radio, Rothstein argued it will be difficult for the state to obtain the drugs necessary to ensure Addison is not subject to pain and suffering.

Because New Hampshire has never put anyone to death by lethal injection, the state has not developed proper procedures or protocols, he argued.

State law says executions can be carried out by hanging if it is impractical to use lethal injection. Rothstein argued death by hanging “offends contemporary norms and standards of decency.”

The filing mentions recent executions in Ohio, Arizona and Oklahoma, where lethal injection procedures caused the people being put to death to gasp for air or writhe in pain.

Legislative efforts to repeal the death penalty over the past decade have failed.