Roderick Knox on Tuesday testified he never had a sexual relationship with the 15-year-old and that she lied.
The Press of Atlantic City reports Knox claimed he told the girl he would notify her caseworker after she said she was sexually attracted to him in 2010.
Knox's wife testified that she called the girl a liar.
The girl testified that she had sex with the 47-year-old four times.
Knox, who has been suspended from the Fire Department without pay for more than a year, is charged with aggravated sexual assault, criminal sexual contact and child endangerment.