Telling employees where and why cameras are being used in the workplace is the best way to avoid legal problems, according to Lisa Guerin, co-author of "The Essential Guide to Federal Employment Laws" (Society for Human Resource Management/Nolo, 2011).

There is implied consent if an employee continues to work in an area where a camera is visible, said Ginger McCall, director of the open government program at the Electronic Privacy Information Center in Washington, D.C.