In a letter to Air Force Secretary Michael Donley and Air Force Chief of Staff Mark Welsh III, McCaskill, a member of the Senate Armed Services Committee, questioned a decision by Lt. Gen. Craig Franklin -- commander of the 3rd Air Force -- that evidence presented in the court-martial of Lt. Col. James Wilkerson did not prove guilt beyond a reasonable doubt.
Wilkerson, was the 31st Fighter Wing inspector-general when he was charged in 2012 with groping a guest at his home near Aviano Air Base in Italy. A jury at Ramstein Air Base in Germany convicted Wilkerson in November of aggravated sexual assault and sentenced him to one year in prison and dismissal from the Air Force.
The 3rd Air Force said in a statement Wilkerson was released Feb. 26 from a military jail in Charleston, S.C., and the process of returning him to "full-duty status" was under way, Stars and Stripes reported Tuesday.
McCaskill said in her letter to Donley and Welsh Franklin's decision undermines the Air Force's current effort to "erase a culture that has often turned a blind eye on sexual assault."
"His decision shows ignorance, at best, and malfeasance, at worst. I strongly urge you to undertake an immediate review of his conduct and consider removing him from his leadership position."
Sens. Barbara Boxer, D-Calif., and Jeanne Shaheen, D-N.H., urged Defense Secretary Chuck Hagel in a letter Monday to "immediately provide us detailed information regarding the basis for General Franklin's decision, including whether you have the authority to overturn the dismissal of the case."
"In addition, we urge you, in the strongest possible terms, to take immediate steps to restrict Convening Authorities from unilaterally dismissing military court decisions," Boxer and Shaheen wrote.
Stars and Stripes said military sexual assault victim advocates have argued the kind of discretion exercised by Franklin enables offenders and deters victims from reporting assaults.
McCaskill brought up the matter at a Senate hearing Tuesday, saying she questioned whether, "after this incident, there's any chance a woman assaulted in that unit would ever say a word."
"And what this decision did -- all it did was underline and put an exclamation point behind the notion that if you are sexually assaulted in the military -- good luck," she said.