Apply for a job or promotion these days and chances are you'll go through a criminal background check.

But what happens when the information it uncovers is wrong and you don't know it?

KIRO 7 Eyewitness News reporter Graham Johnson has a warning for anyone applying for work.

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Criminal background checks are supposed to keep child molesters from working with kids and thieves away from jobs as bank tellers.

But sometimes, people with clean records lose jobs.

"I've never been arrested. I've never been in trouble," said Tracey Woods.

Woods not only avoided run-ins with police, she worked for them.

For 20 years, Woods did clerical work for the assistant chief of the St. Louis city police department.

"You can't do two things. You can't be a criminal and work for the police department."

Woods says she lost her job when a new boss eliminated her position.

Nine months later, she was hired at Fed-Ex. But before she could report for work, a background check flagged her as a convicted felon.

"It does list the person who was arrested and all of the aliases they ever used and one included my name," Woods said.

It turns out the person arrested was her sister. Sheila Hollins had the criminal record.

"She has a very nice one -- a very nice criminal record under my name," said Woods.

Before she was murdered in 2000, Hollins stole her sister's identity.

Tracey Woods only learned that when she applied at Fed-Ex. The company Fed-Ex hired to check her background is Intellisense, based in Bothell.

Intellisense requested records from the state of Missouri.

"We provided a name, date of birth, Social Security number, address and they submitted it back to us as a hit and this was a positive ID," said Rhonda Taylor, IntelliSense President.

Shocked by the findings, Woods did her own search and sent Intellisense what she found.

"I faxed her both the city and the county records check that says I have no record. I sent her a copy of the obituary. I sent her a copy of the death certificate and she politely told me I had to prove it was not me."

Intellisense says it cleared up the confusion within five business days. By then, Fed-Ex gave the job to someone else.

"We almost did Tracey a favor because we alerted her to the information we found, provided her the information so she could go ahead and dispute it and get it cleaned up so it wouldn't affect her in the future," Taylor said.

Intellisense says its error rate is less than half a percent. But consumer advocates warn the industry has an accuracy problem.

"These background check companies for employment are only in their infancy and their practices are very loose," said Evan Hendricks, Editor of Privacy Times. "They're willing to sell information about you that they've never checked to see if it's accurate."

Hendricks says screening companies often do nothing more than a database check.

"They never interact with you and they never check with you to see if its accurate. And at the end of the day, the information is only as good as they source they get it at," Hendricks said.

Federal laws on background checks depend on who conducts them.

If you apply for a job at a place that contracts with an outside company, you must give your consent.

And if you're rejected because of something screeners find, you must be told.

But those protections don't apply if an employer does its own background check.

After her experience, Tracey Woods has this advice to anyone looking for work:

"Find out before anybody else finds out what's on your name so that you can correct it."

Fed-Ex won't comment on Tracey Woods' case, but a spokesman says anyone rejected because of a background check error is welcome to re-apply once the record is clear.

There are several companies now offering ways to check your own background, but you should know some of the more comprehensive searches cost as much as $100.