MIDDLEBURY, Vt. (AP) — A Texas man is facing charges alleging that he posed as a medical researcher in order to sexually assault a Vermont college student.

NECN reports (http://bit.ly/2eY8q6C ) 31-year-old Nam Vu Bui, of Houston, pleaded not guilty Tuesday in Middlebury to charges including illegal advertisement of medical services and sexual assault.

Authorities say Vu Bui was a guest of a Middlebury College student, who believed he was a medical resident at Dartmouth-Hitchcock Medical Center. Police say Vu Bui said he was studying early detection of cancer in women.

Police say Vu Bui asked the woman's friends to take part in his research. They allege he convinced a female student to let him blindfold her. He allegedly videotaped her while touching her.

Vu Bui's attorney says the evidence on some charges is flimsy.