PHOENIX -- We all know there are cameras tracking how we drive, but CBS 5 Investigates found police cameras hidden all across the Valley, keeping an eye on residents and recording what they say and do.

Police used the technology in the Baseline Killer and Serial Shooters cases.

"You look at it, you think it might be a palm tree but in actuality it houses antennas and it houses radio equipment," said Jeff Butler of Firetide, a wireless networking company.

Last summer, police desperately needed to cover more ground.

"Basically the city of Phoenix said, 'Hey, we've got to put something in place. We don’t have enough manpower to track these guys, stake out these guys, and do what we need to do to try to capture or apprehend these guys,'" Butler said.

It was summer 2006 and two separate killers were terrorizing the Valley.

A serial shooter seemed to be randomly taking people out.

A man dubbed the Baseline Killer would strike during the night, grabbing women in the dark. He raped some and killed others.

Phoenix police turned to an unconventional way of covering more with less: high-tech video cameras.

The company that makes the cameras makes a tiny camera that records movements and conversations and can be hidden in just about anything.

It took less than two weeks to install roughly 25 cameras around town.

"I would say in cases like that, I would agree with it," said Phoenix resident Regina Patterson.

"'Big Brother' issue? I mean, how about 'people being killed' issue?" said another resident, Dr. Mark Wong.

"I think it's OK. Kind of a little bit of invasion of privacy, I guess, for everyone else who's not doing anything. But they did what they had to do to catch him, so I'm glad he's off the street," said Phoenix resident Tiffany Tapia.

"How big of a role did these cameras play in helping police catch the Baseline Killer?" reporter Tammy Leitner asked Butler.

"As we understood, they helped immensely in gathering information, a lot of things for the investigation. A lot of this was confidential, which we weren't privy to, nor should we be," Butler said.

Police haven't said exactly how the cameras helped, because they won't talk about the case.

"I don't know to this day that situation. That will probably come out post-trial," Butler said.

So remember that when you cruise the streets of Phoenix, you may not see the police, but they may be watching you.

Don't worry, though, about them catching you jaywalking or littering. The cameras can only be installed for specific cases after police obtain a specific warrant. After each case is solved, the cameras are taken down and moved to a new location.