You can do everything with the SJ4000 cam that the DVR cameras do and a little more at less of a cost. The SJ4000 can be modified to Full Spectrum (which I happen to do), each camera has its own sd card, they can be used with the battery, or take out the battery and use the plug in for power. The SJ4000's can be mobile as well if you ever need to unhook them from the tripod and carry them with you.
If you use the WIFI SJ4000 you can connect them to a tablet or phone as each camera has its own IP address. There are no cords needed, to untangle, run through out the location, wrap up, store, carry back and forth to the locations or tape down or up so no one trips on them.
As for capturing evidence, like I said they can be modified for full spectrum, they record both audio and video, they record in 1080p which means no more black and white grainy video to review just color hd. And they do have a time stamp on the video as well.
So now you see why teams are changing over to the SJ4000 cams instead of the old DVR systems. Cordless is so much better.