TORONTO - A decision on whether so-called sound cannons can be legally used against G20 protesters will come Friday.
An Ontario judge is hearing arguments today from two civil rights groups that want an injunction preventing their use.
Lawyer Paul Cavalluzzo says Toronto residents should not be used as "guinea pigs" to see whether the sound cannons are safe.
Cavalluzzo says the devices have the potential to permanently damage hearing.
He accuses police of relying on manufacturer studies about safety, rather than independent research.
Lawyers for police will make arguments later today, and the judge says he'll deliver his decision Friday morning.
Toronto police have purchased four sound cannons, which can emit piercing noises similar to a smoke detector.
Police say they will use them to broadcast pre-recorded messages to protesters.