In Wisconsin, Audrey Edmunds served 11 years in prison in the shaking death of an infant girl for whom she had been baby-sitting. In 2008, a mountain of new medical evidence cast so much doubt on the case that a higher court overturned her conviction and set her free. Leaving prison, Ms. Edmunds hoped that would be the end of it.

But a few months later, as she applied for a secretarial job with an office-supply company, her conviction for first-degree reckless homicide popped up in a background check. Sorry, she was told. She tried to get work with an airline, but heard a similar rejection.

“I hate it,” said Ms. Edmunds, 52, who now lives in northern Wisconsin. “They put us through enough to begin with. They don’t give us any assistance. I’m glad to be out, but there’s got to be more support. I don’t like having this awful nightmare of a cloud hanging over me.”

Across much of the country, sealing or clearing a criminal record after a wrongful conviction is a tangled and expensive process, advocates and former prisoners say. It can take years of appeals to courts and pleas to governors to wipe the slate clean. Even then, many felony convictions remain on federal databases and pop up during background checks or at traffic stops.