When Pennsylvania prosecutors asked Donna Motsinger if she would testify against Bill Cosby at his sexual assault trial next summer, the 74-year-old great-grandmother didn't have to think it over.
"I said yes and I didn't hesitate at all," Motsinger told NBC News. "If there's any way I can bring some kind of closure for all these victims, what kind of a person would I be if I said no?"
Motsinger, a retired motel operator who lives in New Mexico, is one of 13 women prosecutors hope to bring to the witness stand to prove a pattern of behavior by Cosby. A judge has not yet ruled on whether they can testify.
In a motion filed earlier this month, the Montgomery County district attorney didn't use the women's names but provided details that match the accounts some of Cosby's accusers have given in interviews since the sex-abuse scandal erupted.
It appears all but two of the 13 women previously have gone public about encounters with Cosby, although not all of them were willing to talk now about the prospect of testifying.
Dozens of women have accused Cosby of sexual misconduct spanning decades, but he faces criminal charges in only one case, stemming from allegations by Andrea Constand that he drugged and molested her in 2004.
Cosby, 79, has denied any wrongdoing and has filed defamation lawsuits against some of his accusers.
Prosecutors in the Constand case said in court papers that they investigated nearly 50 accusers and "what became clear was that defendant has engaged, over the course of his lifetime, in a pattern of serial sexual abuse."
The allegations of other women, they argued, will show the jury that Cosby's behavior with Constand was not a one-time mistake but part of a "common plan, scheme or design."
Prosecutors did not say how they chose the 13 women from the larger group, but all of those described in the motion say they were drugged. Seven allege that they consumed spiked drinks; six say they were given pills before being assaulted.
In Motsinger's case, Cosby befriended her and her son in the early 1970s when she was a waitress at a California restaurant he liked, according to the motion.
After inviting her to a show, he gave her wine in the limo and then gave her a pill for a headache, prosecutors charged. She was incapacitated and could not resist his "unwanted sexual advances" as she drifted in and out of consciousness, the motion says.
Motsinger was one of the Jane Doe accusers listed in Constand's 2005 lawsuit against Cosby, which was settled out of court. She told her story publicly in late 2014 but said she has tried to reclaim her privacy since then.
"This isn't something that's easy for somebody as private as I am but it's something I have to do. I feel like it's my responsibility to do whatever I can for all the victims," said Motsinger.
Heidi Thomas, a former model, said she also was approached by prosecutors in the Constand case about testifying.
"I said, 'In a New York second,' " Thomas told NBC News.
Although she was not informed she was one of the 13 chosen, her account appeared to match the details given for one of the accusers in the motion.
In 1984, the aspiring actress accepted an invitation to see Cosby at Harrah's in Nevada but was instead whisked by a driver to a house in Reno where the comedian was waiting, the motion says.
He asked her to read a script for the role of a drunk person, and gave her an alcoholic beverage. After she drank it, "she became incapacitated," and Cosby forced her into oral sex as she faded in and out, prosecutors said.
Thomas said she is willing to tell that story in a courtroom, and face cross-examination by Cosby's attorneys, to bring more attention to the issue of assault assault and to show unity.
"I don't know Andrea but she's one of us and we want to support her however we can," Thomas said.
Under Pennsylvania law, prosecutors can introduce evidence of a defendant's so-called “prior bad acts” to demonstrate his intent or modus operandi, said Wes Oliver, NBC News legal analyst and criminal justice program director at Duquesne University.
In Cosby's case, Oliver said, the message is "if 13 women say he raped them, then what are the odds the 14th one is lying?”
It appears that two of the women in the motion have not publicly accused Cosby.
One was an aspiring actress who worked at a Playboy club when, she told prosecutors, she met Cosby in the early 1970s. He allegedly invited her to dinner, gave her Quaaludes and champagne in his limo. She says she awoke naked in a hotel bed.
The other was a flight attendant who met Cosby on a plane in 1964 and struck up a friendship, the motion says. After being given a role as an extra in his show, she was taken by limo to a hotel room, where he allegedly gave her spiked champagne and assaulted her as she lost consciousness, prosecutors said.
Cosby's attorneys are sure to oppose the motion to admit prior bad acts but have not yet filed a response. A spokesperson declined to comment on the 13 women's accounts, directing NBC News to statements made by defense lawyers outside court after his last hearing.
The attorneys said then that Cosby's civil rights are being trampled because he's black and they complained about a "barrage of new accusers claiming 'me too.'"
"For Mr. Cosby, this is a version of the 'shoot now, ask questions later' approach to judicial justice," said lawyer Angela Agrusa.