COLUMBUS, Ind. -- A central Indiana school corporation has stopped utilizing a substitute teacher after learning that she admitted under oath that she had a drug addiction.

The Bartholomew Consolidated School Corp. had entrusted Teresa Estes (pictured), 43, to educate its students, but school officials admitted they made a mistake, 6News' Jack Rinehart reported.

In August, Estes said under oath as a witness in a conspiracy to commit murder trial that she had spent much of her life on alcohol and drugs and began using at age 14.

"I would come to Indianapolis to purchase drugs and go back to my hometown," Estes testified in that trial.

When she was asked if she had an addiction to crack cocaine, Estes responded, "I suppose."

Estes also testified that she worked for the school corporation as a substitute teacher, but that information was apparently not immediately shared with the school district.

This year, Estes had worked six days in the county's elementary schools. Last year, she taught more than 40 days.

"Every now and then, you get caught off-guard and surprised, and this surprises us greatly," said Larry Perkinson, the school system's student assistance coordinator. "Somebody who has an addiction issue puts others in harm's way, potentially."

Estes testified that she never smoked crack during a school year, but 6News found that three months into the 2007 school year, Columbus police stopped Estes on suspicion of speeding and driving on a suspended license.

Police said they found a glass pipe and cocaine in the car, and in a police report, the officer said that Estes admitted that she had just smoked crack.

According to court records, prosecutors dropped the cocaine charge in March 2009 after Estes agreed to plead guilty to possession of marijuana.

Estes got a suspended sentence, probation and a court order to stay off alcohol and drugs for at least a year.

When the court records were shown to the Bartholomew County Probation Department, they began investigating whether Estes might have violated her probation after the August admission that she had smoked crack.

Thursday afternoon, Bartholomew County prosecutor filed a petition to revoke Estes' probation after she failed a recent drug screening, testing positive for methamphetamine.

Bartholomew Consolidated Schools randomly drug-screens students and transportation workers, but not teachers.

"I get drug-screened working in a factory. I think they should have random drug screens here," said one resident.

In the 2007 drug arrest, Estes listed her profession as substitute teacher, but probation officers never passed that information to the school. In the 2009 trial, police, prosecutors and court staff kept silent, too, Rinehart reported.

School administrators said they conduct background investigations on all teachers, but they don't have a policy that requires employees to report arrests and convictions after their hiring.

"I am aware that when they fill out for employment, it asks if you have been convicted," Perkinson said. "There's a statement on the application, but not one that says afterward that you'd be required (to report subsequent arrests or convictions)."

6News reached Estes by phone, but she declined a request for an on-camera interview.

The school district said it has removed her from the substitute teacher rolls.

The prosecutor filed a petition Thursday to revoke Estes' probation. Based on the transcript of her testimony at trial, officials called her in for a drug screen in which she tested positive for methamphetamine.