Debra Lafave, 24, was under such emotional stress that she didn't know right from wrong when she had sex with a 14-year-old student numerous times in June 2004, attorney John Fitzgibbons said after a brief court hearing. A Dec. 5 trial date was set.
Both sides said they had hoped to avoid a trial, reports Dave Balut of WTSP-TV in Tampa.
Fitzgibbons said plea bargaining broke down because prosecutors wanted too much prison time for Lafave, who appeared in court Monday but did not speak.
"To place an attractive young woman in that kind of hellhole is like putting a piece of raw meat in with the lions," said Fitzgibbons, who wouldn't talk about details of the negotiations. "I'm not sure Debbie would survive."
He said he had hoped to settle the case with a plea agreement, "not only for Debbie's sake but for the young man's sake."
State attorney's office spokeswoman Pam Bondi also wouldn't disclose details of the negotiations but said prosecutors "made every effort to resolve the case, and now we will have to put the victim and his family through a trial."
"Our interest was in trying to spare the victim from having to testify in this case, and we made the best offer we could under the circumstances to try to accomplish that," said prosecutor Mike Sinacore.
Judge Wayne Timmerman agreed to appoint two mental health professionals to evaluate Lafave, who Fitzgibbons said would claim she is not guilty by reason of insanity.
"What teacher in her right mind would do something like this?" Fitzgibbons said.
She is charged with four felony counts of lewd and lascivious battery and one count of lewd and lascivious exhibition. Each carries a maximum 15-year prison term.
Prosecutors have said that a state psychologist already determined Lafave was not insane at the time, while one hired by the defense concluded that she was mentally ill.
The teen told investigators that he and Lafave, a newlywed at the time, got to know each other on their way back from a class trip to SeaWorld Orlando in May 2004.
He said she invited him to her class during detention and ended up taking him to his basketball practices at a recreation center, to get his hair cut and to his house, court records said. The sexual relationship allegedly began on June 3, 2004.
The boy told investigators the two had sex in a classroom at Greco Middle School in Temple Terrace near Tampa, her Riverview town house and once in a vehicle while his 15-year-old cousin drove them around Marion County. He said Lafave told him that her marriage was in trouble and that she was aroused by the fact that having sex with him was not allowed.