CHICAGO � State lawmakers crafting legislation that would govern the use of body cameras by police officers got a glimpse Friday of a complicated debate as proponents of the devices in and out of law enforcement raised questions about issues ranging from privacy to cost to public trust.

In a lengthy hearing, the Illinois Judiciary Committee listened as police chiefs said they were eager to join the growing ranks of police departments that have started using cameras, a trend that has picked up speed since August, when a police officer who was not wearing a body camera shot and killed an unarmed teenager in Ferguson, Missouri.

They said they were encouraged by the handful of studies of the use of the cameras that have shown the number of excessive force complaints has fallen dramatically � something they attributed to both the improved behavior of officers who know the cameras are rolling and members of the public who are less likely to file complaints because they know the cameras would reveal officers acted properly.

But they said they were reluctant to go forward out of concern with the new privacy legislation that lawmakers are working on in response to the Illinois Supreme Court�s ruling that the state�s eavesdropping law was unconstitutional. They worry that this could force them to scale back or abandon the use of cameras.

�We want to be able to use these cameras, but we need the legislature to tell us how we can use them,� Fred W. Hayes, president of the Illinois Association of Chiefs of Police and the chief in the small community of Elwood, said before the hearing.

But they also suggested that there might be reasons why they would not want to follow so many other departments and start using the cameras. At the top of the list is their contention that the state has to give them some discretion to decide when the officers must turn on their cameras and when they can turn them off, and whether they will be legally bound to make the footage, some of it highly embarrassing, available to the public.

�Where is the public good in that type of sensationalism?� asked Pat Hartshorn, Vermilion County Sheriff and a past president of the Illinois Sheriffs� Association. �It�s turning officers into unwitting paparazzi.�

And they said there is no reason why activities ranging from undercover operations to bathroom breaks should be recorded.

But others said they were worried that giving the officers that kind of discretion is inviting abuse by the officers and could actually increase public mistrust of the police.

�Once you do that, you open up the spigot of misuse of the camera,� said Harvey Grossman of the American Civil Liberties Union of Illinois.

Just what legislation would look like is unclear.

State Sen. Kwame Raoul, a Chicago Democrat who co-chaired the hearing, said lawmakers do not want to �get into the weeds� on the policies of individual departments. But he said it is imperative that the state address some key issues, starting with privacy and which encounters with police the public has a right to see and which ones those involved have a right to keep private.

�There ought to be a broad kind of framework as to how it should be done because we are a state that has a more heightened protection for individual privacy,� he said.

Raoul said the use of body cameras is one of the final and crucial pieces to new eavesdropping legislation lawmakers are working on.