WASHINGTON — The woman who has accused Lt. Gov. Justin E. Fairfax of Virginia of sexual assault came forward on Wednesday, issuing a statement through a law firm that described a 2004 encounter at the Democratic National Convention in Boston that, she said, began with kissing but quickly turned into an episode of forced oral sex.
Mr. Fairfax, who has retained lawyers to assist him, has emphatically denied the allegation and argued that there is no corroborating evidence to support it.
Late Wednesday night, aides to a prominent Democratic Virginia congressman, Bobby Scott, said that the woman told him a year ago that she had made an allegation of sexual assault against Mr. Fairfax.
She is Vanessa C. Tyson, an associate professor and expert in black history at Scripps College in California. She has also spent years advocating for victims of sexual assault and has spoken openly about being molested by her father when she was a child.