Christopher Drew is a 60-year-old artist and teacher who wears a gray ponytail and lives on the North Side. Tiawanda Moore, 20, a former stripper, lives on the South Side and dreams of going back to school and starting a new life.

About the only thing these strangers have in common is the prospect that by spring, they could each be sent to prison for up to 15 years.

“That’s one step below attempted murder,” Mr. Drew said of their potential sentences.

The crime they are accused of is eavesdropping.

The authorities say that Mr. Drew and Ms. Moore audio-recorded their separate nonviolent encounters with Chicago police officers without the officers’ permission, a Class 1 felony in Illinois, which, along with Massachusetts and Oregon, has one of the country’s toughest, if rarely prosecuted, eavesdropping laws.