Hi. In drivers ed tomorrow, I am a lawyer in a DWI mock related accident. I need questions to ask to witnesses, the driver, family etc/ here is the scenario:

I am the lawyer, defending a
73 yr old man charged with DWI of a intoxication level of .30. He survived, wife in passenger seat died. He crashed into a Coach Bus driver, with 12 people on his bus, 4 people died which includes the driver of the coach bus. The Bus driver was also drinking and taken drugs (not sure the amount, maybe marjiuana, weed etc).

I have to come of with questions for the:
The 73 yr old man
The 73 yr old mans family, kids grandkids, etc.
The surviving 9 passengers buy prozac online on the bus.

What are some good questions to ask? also, what could I do to prove my clients not the only fault to this accident?