A Louisiana woman blames a false positive field drug test for ruining her life, and now she's suing the City of Houston, Harris County, a former district attorney and two police officers for $2.5 million.

"It practically took my whole life and turned it upside down," said Amy Albritton. "People who haven't been through this have no idea."

In 2010, Albritton brought her son, who has cerebral palsy, to visit a doctor in Houston. While he was at the hotel, she and a friend went out to get some food. They were pulled over by Houston police.

"They said we didn't turn our blinker on," Albritton said.

The routine traffic stop turned into something more when officers spotted a white substance in the vehicle they believed was crack cocaine. The officers put a sample of the substance in a field drug test kit, and the kit indicated it tested positive for narcotics.

"I knew there was no cocaine in that car. I was innocent," Albritton said.

Albritton was booked into the Harris County Jail and says she was encouraged by a public defender to take a plea deal.

"He just said it was either two years' hard labor or 45 days in jail," she said.

Albritton says she was worried about her disabled son and wanted to get back out quickly to be with him.

"I remember the lady judge asking me several times, 'Are you sure you want to plead guilty?'" Albritton said. "I didn't think I had a choice."

She was served 21 days in jail, but says her nightmare was just the beginning. The guilty plea caused her to lose her job.

"The jail experience was pretty bad," Albritton said. "But when I got out of jail, I realized I had no home, no car, I lost everything."

But field drug tests, like the one that sent Albritton to jail, aren't always accurate. In fact, the test manufacturers and the Department of Justice say suspect samples should always be tested again by scientists in a crime lab.

Six months after her arrest, the Houston crime lab tested the sample found in Albritton's car. They determined it was not a controlled substance. There were no drugs in Albritton's car, but it would take years for her to find out authorities had proof she was innocent.

It took three years for the Harris County District Attorney's office to send her a letter, saying she was convicted in error. The letter was sent to Albritton's old address, so she never received it. It took another year for her to find out she was cleared.

"I was like, 'Thank you God,' because I knew I had not done that," Albritton said.

Inger Chandler heads up the conviction integrity unit for the Harris County DA's office. While she can't comment specifically on Amy's case, she says the office is aware there was a problem.

"The idea that we get it wrong and the system sometimes gets it wrong can rock you to the core," Chandler said.

Chandler says she uncovered more than 300 cases where lab results proving someone's innocence simply sat in unread emails. In some instances, the crime lab was sending the results, but nobody at the district attorney's office was seeing them. Chandler says that problem has been fixed.

She says the DA has worked with the public defender's office and helped clear 140 people who originally pled guilty to drug crimes, even though there were really no drugs found.

"When you have so many humans involved in something, you have room for human error," Chandler said. "That's honestly what we found."

Chandler says it can be tricky to locate many of these individuals because they tend to move around a lot. So far, they have cleared 140 of these cases.

The district attorney's office has also changed its policy on accepting guilty pleas before confirmatory lab results are returned.

While Albritton's name has been legally cleared, the arrest is still on her record. She says it has made it tough to find jobs.

"We have not had a home since this happened. I have not had a job with insurance since this happened," Albritton said. "Words can not express how this has traumatized my life."

Albritton's attorney agreed to take her case on for free.

"When Amy told me her story, it was a story I could not walk away from," said attorney Richard Werstein. "Her life has been ruined since the day those lights went on behind her."

Harris County and the City of Houston referred us to their attorneys, who declined to comment for the story. In court filings, they argue that Albritton could have checked public court records herself, to find the DA's letter, indicating she was innocent. They also argue that the statute of limitations has run out.

But Albritton says she is moving forward with her case, making sure this doesn't happen to someone else.

"It's despicable to me. I just don't see how they can do this to people and sleep at night," Albritton said. "What if it was their mother, their sister? How would they feel it if happened to them?"