There are two basic insurance principles involved: (1) losses resulting from intentional acts aren't insurable; and (2) losses resulting from illegal acts aren't insurable.
I think some of the technical, insurance issues can probably be handled by the carrier reimbursing criminal defense costs only when the defense is successful. (Which is still better for the insured than not getting anything, ever.) But it doesn't resolve the public perception issue.
I can't imagine that any automobile insurance policy will cover the defense of e vehicular manslaughter charge. All the policies I've seen exclude such expenses and cover only defense of civil suits and damages awarded in civil suits.
And IIRC Washington State as a strong self defense immunity law. If one is charged criminally as a result of a use of force claimed by the defendant to have been in self defense, and if the defendant is acquitted, the defense costs are recoverable from the State.
I'm not going to look at up now, but I seem to recall some discussions along those lines here or at THR.