James Hooker, 42, is facing one count of oral copulation with a person under 18 in connection with an alleged 1998 encounter.
His attorney, Mary Lynn Belsher, argued during a hearing on Tuesday that the charge should be dismissed, saying the statute of limitations has expired, the Modesto Bee reported.
A Stanislaus County judge is expected to rule on that request on Oct. 23. The preliminary hearing was delayed, although the alleged victim did testify.
Hooker made national headlines earlier this year when he left his family and job to move in with his former student at Modesto's James Enochs High School, 18-year-old Jordan Powers.
Hooker and Powers insisted on talk shows and during news interviews that they did not have any sexual contact until Powers turned 18.
Police investigated that claim they uncovered Hooker's separate 1998 relationship with a girl who was then 17.
Now 31, the person testified that she and Hooker met at a conference when she was a student at a Modesto high school and he was a business teacher at another school in the city.
They exchanged romantic notes and talked about wanting to spend time together, she said, adding the relationship ended when Hooker told her that his wife had discovered an incriminating email.
A judge has entered a not guilty plea on Hooker's behalf. The Bee reported that he shook his head and wrote on a yellow legal pad as the woman testified.
The woman said she decided to come forward after learning about Hooker's relationship with Powers and realizing he had not returned to his family.