A free market approach would be something like legal insurance which would have high deductibles and cover catastrophic legal expenses - like a murder trial.
There may be something in that. However, like an insurance policy which won't pay out if you commit suicide just to give your wife a chunk of cash, I think legal insurance would have boundaries.
If I buy insurance in Jan and kill my wife in Feb, I don't think the insurance company will be happy paying for a full legal defense with all the bells and whistles. But, since I'm entitled (I guess) to legal representation, we're back to the original question of access.