"As the senator works to change the military justice system to better protect survivors of sexual assault and hold perpetrators accountable, she wants to ensure that cases in which commanders overturned jury verdicts against the advice of legal counsel are given the appropriate scrutiny," Drew Pusateri, a spokesman for the senator, said Thursday.
In February 2012, Helms rejected the recommendation of legal counsel and overturned the conviction of an Air Force captain who had been found guilty of aggravated sexual assault of a female lieutenant.
McCaskill's hold prevents the Senate from approving Helms' nomination.
The Helms' situation echoes another Air Force case that has outraged members of Congress.
Lt. Gen. Craig Franklin, commander of the 3rd Air Force at Ramstein Air Base in Germany, overturned the conviction against Lt. Col. James Wilkerson, a former inspector general at Aviano Air Base in Italy. Wilkerson had been found guilty last Nov. 2 of charges of abusive sexual contact, aggravated sexual assault and three instances of conduct unbecoming of an officer and a gentleman. The incident had involved a civilian employee.
Wilkerson was sentenced to a year in prison and dismissal from the service, but after a review of the case Franklin overturned the conviction.
Lawmakers demanded a fresh look at the military justice system. Earlier this month, Defense Secretary Chuck Hagel recommended that military commanders be largely stripped of their ability to reverse criminal convictions of service members.
McCaskill, a member of the Senate Armed Services Committee, has introduced legislation that would limit the authority of military commanders to overturn convictions.