WASHINGTON — It's often the toxic ingredient of a military rape allegation: binge drinking. Many times, the woman knows the man and was drinking alcohol with him. Lots of it.
As a result, she says she doesn't remember the entire encounter because she was drunk. Sometimes, she's not even sure herself whether she was sexually assaulted. The man says it was consensual. No other witnesses can say either way.
Determining what happened can be a challenge for the most experienced lawyer, let alone a jury.
"These cases are incredibly difficult to prosecute," said Teresa Scalzo, a veteran civilian prosecutor and the deputy director of the Navy's Trial Counsel Assistance Program.
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"People tend to believe that sexual assault is a stranger jumping out of the bushes and using a lot of force. What we're dealing with on a daily basis is where do you draw the line between drunk sex and sexual assault?"
Under a 2006 law, the military can seek charges of sexual assault if the victim was "substantially incapacitated" from drinking too much alcohol. Judges and juries are told that means the victim couldn't "appraise the nature of the sexual conduct," communicate unwillingness or make competent decisions. The military defines that level of intoxication as "well above" drunk driving limits, but it doesn't say exactly what it is.
Military judges, meanwhile, have assailed the law that created the new definition as confusing and possibly unconstitutional.
Earlier this year, for instance, the U.S. Court of Appeals for the Armed Forces dismissed charges against Stephen Prather, an Air Force enlisted man who'd been found guilty of sexually assaulting a woman in a drunken encounter. The court concluded that the law had resulted "in an unconstitutional burden shift to the accused."
Making the legal decisions more complicated, the facts in such cases can seem so distorted by blurry memories that even military lawyers disagree over the right legal course.
In a 2008 case, the military pursued sexual assault allegations against Marine Capt. Nicolas Stewart even though a lawyer who'd evaluated the evidence recommended against it.
Stewart was accused of sexually assaulting a longtime friend while she was drunk. She'd had sexual relations with the Marine previously, but not intercourse.
In an emotional email, the woman confronted Stewart, saying she was upset about the encounter, but she added, "you probably did not mean any disrespect and thought that you were not crossing the line."
"I realize we have a past and we were both drunk but that does not give you the right to come into my bed without an invitation," she wrote. "I do not want you to think I am someone you can hook up with every now and then for fun."
Stewart, a fighter pilot at the time, apologized for crossing "the friend line" with the woman and worried that another woman he was dating would find out.
After she responded that he didn't seem to understand that she felt violated, he begged her forgiveness.
"Do you think I did something that I can't even bring myself to say, or do you think it was something that happened between two extremely drunk people?" he asked in an email.
"Please, please tell me that you don't think I was forceful with you. Although I can't imagine that I was, I can't remember."
The woman responded: "Do I think you came into my room and pinned me down and forced me to do things against my will? No, I truly do not. I can't even say I told you 'No' or that I even tried to push you away."
But she added: "In my eyes, I was asleep when everything happened. And you did not have my permission."
The woman later testified that the only reason she'd realized they'd had intercourse was that she recalled Stewart telling her they didn't use a condom and asking her whether she was on birth control pills.
Thomas Bowers, an attorney who reviewed the case for the military, recommended that the charges be dismissed because, he said, "reasonable grounds" didn't exist to believe that Stewart had sexually assaulted the woman. Bowers reviewed the case as the investigating officer during an Article 32 evidentiary hearing.
"This is a difficult case with many inconsistencies and many unknowns," he wrote.
Bowers said he didn't think there was enough evidence to indicate that the woman was "substantially incapacitated" under the law.
The only physical evidence that the encounter might have gone too far, he noted, was a copy of a photo of a purported bruise on the woman's leg. Bowers said it was "of no value" because it was of such poor quality and wasn't taken by investigators.
"There are no winners in this matter," he said. "I believe a degree of trust was broken, that a friendship was forever changed or shattered and that both parties have significant remorse for their actions."
Pressed by the woman's parents to take legal action, Stewart's commander sent the case to a court-martial to let a jury decide.
In 2009, Stewart was convicted. The military jury sentenced him to two years in prison and discharged him from the Marines.
The case remains unresolved, however. Next year, the U.S. Court of Appeals for the Armed Forces will hear Stewart's appeal, which includes questions about the constitutionality of the law.
(Tish Wells contributed to this article.)
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