A Chicago woman was acquitted Wednesday of felony eavesdropping charges for recording two police officers on her BlackBerry phone without their consent.

The case points to a legal gray area, in which the recording was clearly against state law, but a jury acquitted Tiawanda Moore because it felt she was trying to expose wrongdoing within the department. The two internal affairs investigators were allegedly trying to pressure her to drop a complaint she had filed against a Chicago police officer who she said had fondled her and given her his personal phone number after he responded to a domestic disturbance call in her home.

During the four-minute recording, which the jury played several times before voting to acquit, Officer Luis Alejo is heard telling Ms. Moore he could “almost guarantee” she would no longer hear from the offending officer if she decided to drop her complaint.

Based on statements like that, juror Ray Adams told the Chicago Tribune the jury felt the officers’ behavior “bordered on criminal and [Moore] had the right to record" the conversation.

The Chicago case is reflective of a growing number of cases where police are put on the defensive against citizens who are increasingly using their mobile devices to create video and audio records of their interactions. Police advocates say audio recordings violate the privacy rights of the police. They also say audiotapes often lack context and can be edited to reflect a specific point of view.

Moore was arrested when the officers speaking to her at police headquarters discovered that she was recording them on her BlackBerry device. She was charged with two counts of eavesdropping and spent two weeks in jail before making bail. Before Wednesday’s verdict, she faced up to 15 years in prison.

While videotaping officers while on duty is allowed, state laws nationwide vary regarding audio surveillance. Most states prohibit ordinary citizens from secretly taping other people and require that at least one person in the party be notified to make it legal.

Illinois is one of 12 states that require the consent of every person involved in the conversation, whether it takes place in person, on a phone, or on the computer. (The others are California, Connecticut, Florida, Maryland, Massachusetts, Michigan, Montana, Nevada, New Hampshire, Pennsylvania, and Washington, according to the National Conference of State Legislatures.)

“I’m ordinarily on the side of people being able to observe and … make assessments and criticism of police. That’s part of a healthy democracy and criminal-justice system," says Tom Nolan, a 27-year veteran of the Boston Police Department and a former criminal-justice professor at Boston University. "But I don’t think we’re at a place yet where anyone at any time can audiotape conversations with police, because they become subject to manipulation and interpretation."

Mr. Nolan said Moore’s arrest was justified because her actions constituted a felony. But her lawyer, Robert Johnson, said she “was exempt” from the law because she suspected the investigators were acting criminally.

He suggested the eavesdropping law needed to be modified to protect citizens from future harassment, and that the existing penalties under the current law are “ridiculous.” “It would be one thing if it was a misdemeanor, but to make it a Class 1 felony is totally and completely outrageous,” he says.

Pat Camden, a spokesman for the Chicago Fraternal Order of Police, says the Moore case is not enough to change the law. “The overwhelming majority [of police officers] conduct themselves now knowing there’s a good possibility that they are being recorded,” he says. “The smart officer should be on the street conducting themselves like they’re being recorded anyway, even if they’re not.”