WASHINGTON — The Senate overwhelmingly approved a bill late Monday making big changes in the military justice system to deal with sexual assault, including scrapping the nearly century-old practice of using a ‘‘good soldier defense’’ to raise doubts that a crime has been committed.
On a vote of 97 to 0, the Senate rallied behind a bipartisan plan crafted by three female senators — Democrat Claire McCaskill of Missouri and Republicans Kelly Ayotte of New Hampshire and Deb Fischer of Nebraska — that would impose a half-dozen changes to fight the pervasive problem of rape and sexual offenses that Pentagon leaders have likened to a cancer within the ranks.
‘‘Unanimous agreement in the US Senate is pretty rare — but rarer still is the kind of sweeping, historic change we’ve achieved over the past year in the military justice system,’’ McCaskill said after the vote.
Still, that unanimous support was in sharp contrast to last week, when military leaders vigorously opposed a measure by Senator Kirsten Gillibrand, Democrat of New York, that would have stripped commanders of their authority to prosecute cases and given that power to seasoned military lawyers outside the chain of command.
The Senate voted 55 to 45 for that farther-reaching bill, but that was five votes short of the necessary 60.
Though expressing certain reservations, the Pentagon had been generally accepting of the new bill.
The House could act on the legislation as a stand-alone measure or incorporate it into the massive defense policy bill that it pulls together in the spring.
This ‘‘is not the end of this,’’ Ayotte said in brief remarks on the Senate floor after the vote. ‘‘We will make sure reforms are implemented, commanders are held accountable, and victims are treated with dignity and respect.’’
The new legislation would change the military rules of evidence to prohibit the accused from using good military character as an element of his defense in court-martial proceedings unless it was directly relevant to the alleged crime.
The ‘‘good soldier defense’’ could encompass a defendant’s military record of reliability, dependability, professionalism, and reputation as an individual who could be counted on in war and peacetime.
McCaskill described it as ‘‘the ridiculous notion that how well one flies a plane should have anything to do with whether they committed a crime.’’
The chairman of the Armed Services Committee, Senator Carl Levin, Democrat of Michigan, said Monday that the ‘‘military culture has been slow to grasp the painful truth that even a successful professional can also be a sexual predator.’’
Under the bill, the defense could still be used in the sentencing phase. The Pentagon has indicated that it is crucial as commanders adjust sentences to allow for plea agreements.
The measure also would give accusers a greater say in whether their cases are litigated in the military or civilian system and would establish a confidential process to allow alleged victims to challenge their separation or discharge from the military. In addition, it would increase the accountability of commanders and extend all changes related to sexual assault cases to the service academies.
In cases where a prosecutor wanted to move ahead with a case but a commander disagreed, the civilian service secretary would be the final arbiter. The Pentagon has reservations about that last provision, suggesting it could have a chilling effect on majors and captains if they think every decision gets kicked up to the service secretary.
The Pentagon has estimated that as many as 26,000 military members may have been sexually assaulted in 2012, based on an anonymous survey. Many victims are still unwilling to come forward, the military says.