Well, I recall reading about
this rather freaky tragic accident but I couldn't find with a quick search if criminal charges were eventually filed or not.
This was a pretty extreme case of what seems to me to be negligence in basic trailer safety. The trailer's weight exceeded the rating of its coupler by a few hundred pounds, and the coupler failed, with the trailer running into another vehicle and causing the death of one of the occupants. The trailer ran into the other vehicle after the coupler failed because the safety chains were not attached (or at least not properly attached). The trailer was also not equipped with a breakaway braking system as was required for trailers of its weight in the state. That's at least three basic failures on required common practices. Even so, the charges being considered were "misdemeanor vehicular manslaughter without negligence." The bar for gross negligence is quite high, and this apparently didn't reach it.
I see no indication that the insurance company denied coverage, though that part of things isn't mentioned explicitly one way or the other in the article.