KERMIT, Tex.  It occurred to Anne Mitchell as she was writing the letter that she might lose her job, which is why she chose not to sign it. But it was beyond her conception that she would be indicted and threatened with 10 years in prison for doing what she knew a nurse must: inform state regulators that a doctor at her rural hospital was practicing bad medicine.

When she was fingerprinted and photographed at the jail here last June, it felt as if she had entered a parallel universe, albeit one situated in this barren scrap of West Texas oil patch.

“It was surreal,” said Mrs. Mitchell, 52, the wife of an oil field mechanic and mother of a teenage son. “I said how can this be? You can’t go to prison for doing the right thing.”

But in what may be an unprecedented prosecution, Mrs. Mitchell is scheduled to stand trial in state court on Monday for “misuse of official information,” a third-degree felony in Texas.