<a href="mailto: dvsavini@cbs.com; mhlebeau@cbs.com; mayoungerman@cbs.com" target="_blank">Send Your Tips To Dave Savini</a>By Dave Savini

(CBS) — Police cameras that are supposed to catch criminals are breaking down, and critical evidence is possibly missed.

And cameras that work don’t guarantee an arrests.

CBS 2’s Dave Savini investigates the cameras and videos monitored by Chicago’s Office of Emergency Management and Communications.

In one police camera video, a man runs across the street. Another runs for his life but gets gunned down. The murder was caught on a police camera in March 2012, but the shooter remained free.

Sabrina Freeman’s 26-year-old son Deon was the victim.

“I’m very disappointed,” said Freeman, who did not know the murder was caught on camera until CBS 2 told her.

Such key evidence is a major reason to have police cameras. They have caught everything from wrong-way drivers causing crashes to cab drivers hitting pedestrians to an armored-car bandit who was shot and still tried to get away.

Here is how these cameras are supposed to work: A camera operator, back at OEMC, can follow people to different locations, watch as crimes occur, and even get police dispatched to the scene. The cameras are supposed to help police, but the 2 Investigators uncovered allegations of cameras repeatedly breaking.

Officials at OEMC have refused to turn over details about the cameras, including an audit that details how often they are not working.

“We repair them relatively quickly,” says Gary Schenkel, who heads OEMC. “I couldn’t give you an exact time frame.”

CBS 2 showed Schenkel proof of cameras breaking.

Two Woodlawn cameras, just blocks from where 6-month-old Jonylah Watkins was shot to death in March, were broken the day the baby was killed, says a confidential OEMC source. The source says this was possibly a missed opportunity to record evidence.

“That’s an ongoing investigation, so I can’t comment make any comments on that,” Schenkel responds.

In Freeman’s case, the camera was working, but more than a year passed and no one was charged.

“That’s the category he goes in — just another death in Englewood,” Sabrina Freeman says.

CBS 2 started questioning police about the Freeman murder, and 21-year-old Jamony Nunley was charged.

Police immediately recovered the gun, but prosecutors say police failed to get ballistic results.  We are told, after our calls, police turned over this and other evidence and charges were brought.

OEMC officials say camera repairs can take seconds or days. About one-third of all cameras will be replaced with high-definition and better quality ones throughout the city.

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