I don't know where you are but unfortunately in Texas you can't just take keys away. We went to the DMV filled out reports and they still haven't done anything. I'm sorry your daughter was killed but I think it's the government agency's responsibility to look into people who have problems driving weather they are middle-age or elderly. It's a shame you are blaming this person for their father's decisions because my whole family is in this boat. We've contacted doctors, the dmv, and the local law officers. Now they need to do their job.
We took his keys and he called a lock-smith. The law said if we take his car without permission it is theft and we can be arrested. Again I'm so sorry about your daughter. A friend of my sister killed her when she was just 16 because her friend was a bad fast driver...they didn't even give this person a ticket!