I do DVCam/DVD, MiniDV/DVD and yes sometimes DVD/DVD. Just for kicks I tested a power outage situation again. I record 15 minutes or so, then pull the plug on the recorder...leave it for 5-10 minutes...plug it back in and turn the deck back on. The deck goes into a "repairing" mode for what seems to be an eternity, maybe 10 minutes. I then finalize and I seem to have no loss of information. This has to be about the 4th time I've checked this with different decks and they all work. Maybe I just have special decks but I feel comfortable that I wouldn't be completely SOL in the event of a power outage.
I record to 3 formats at all time. Mini DV, DVD, as well as Capture to Hard Disk with a Laptop. Now because of power failures carry a small Battery backup that powers my DVD and Laptop. Camera has a separate battery on it.
Don't forget audio for the court reporter. It's a common courtesy which is always appreciated even when they are taking .wav files with their laptop mike. If the deponent/lawyers mumble, the audio tapes you give the CR will be much clearer than their .wav files as you ( the videographer) use lavalier mikes and a mixer and can amplify the audio levels. Also do DVD as back-up for 83 minute mini-DV tapes. One client still wants a VHS as back-up which I record onto a SVHS deck with regular VHS tapes but that's the last of VHS I do... Whoops... just saw you asked this question in January! Well, maybe this answer will help someone else.
MiniDV and DVD. I still plug into the wall, use to carry enough batteries to run a basic set up, but never used it. Electrical hum is not an issue, at least it hasn't been for quite some time with my current equipment.
My camera records to mini- DV, and I can back up to either a VHS or a DVD. I can understand the worry that would hit if the power went out and all copies were being captured to devices that can't handle losing power before saving.
Did the power eventually turn back on or was the deposition postponed?