Johannesburg - The city's CBD boasts hundreds of CCTV cameras, but that has not stopped criminals from trying to thwart the efforts of law enforcement."What we have noticed is that they [criminals] change their clothing after they have committed the crime so they cannot be identified easily from the cameras," metro police Chief Superintendent Wayne Minnaar told News24 at the CCTV control room on Rissik Street on Thursday.Those seeking to evade arrest would even change more than once to try and make sure they cannot be identified when arrested."We have a particular incident on camera where a suspect changes twice after a smash and grab where he stole a cellphone. He changes the top and puts it in [a carrier] bag," Minnaar says."Then he changed again and took the shirt off and was only left with a T-shirt by the time the officers arrested him. It's definitely the same man because he's still got the same carrier bag. The system that we use here, we call it a track and trace process."They follow a suspect on foot from camera to camera or from area to area or block to block from camera to camera."Beyond simply changing clothing, criminals have attempted shooting at the cameras, and in one case several years ago, used an angle grinder to cut down the pole the camera was situated on."It was in the middle of the night at one of the Crown Mine hotspots and they used a blanket to cover the camera and they used an angle grinder to cut down the pole," Minnaar says.To stop this from happening, the city has had to install cameras on concrete polls. Procedures were also in place to ensure officers are immediately deployed to cameras that stop working."There was an incident where a guy was shooting at the camera and the operator fell from his chair. As soon as a camera goes down, JMPD goes there immediately to see what happened," Minnaar says.