U.S. Sen. Claire McCaskill (D-Mo.) is holding up the nomination of Lt. Gen. Susan Helms, who is slated to become the next vice commander of Air Force Space Command at Peterson Air Force Base,  Colo., over questions about Helms’s decision to overturn a jury conviction in a sexual assault case.

If confirmed, Helms would become the Air Force’s second highest ranking uniformed officer for space. She is currently the commander of the 14th Air Force and commander of Joint Functional Component Command for Space at Vandenberg Air Force Base, Calif.

“Senator McCaskill has placed a ‘hold’ on the nomination of Lieutenant General Susan Helms, while she waits for additional information about the overturning of a jury conviction in a sexual assault case last year,” McCaskill spokesman Drew Pusateri said via email. “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.”

McCaskill, a member of the Senate Armed Services committee, has proposed legislation that reins in the authority of commanders to dismiss jury convictions against sex offenders. The legislation also would require written justification for sentences that are lessened or commuted. U.S. Defense Secretary Chuck Hagel has supported that provision.

Pusateri said April 30 that McCaskill’s hold, a parliamentary procedure to prevent a motion from coming to the Senate floor, is still in effect.

Lt. Col. Laurel Tingley, a spokeswoman for the secretary of the Air Force, said only that the Air Force was aware of the hold.

Helms is a former NASA astronaut who has spent more than 200 days in space and was inducted into the U.S. Astronaut Hall of Fame in 2011. She was nominated for the new position March 20.