sounds to me it's 100% his fault, and he should pay out of his pocket. his current insurance has nothing to do with that incident. even if it wasn't completely his fault, he wasn't insured, so he has nothing to stand on anyway.

he's gotten into 2 similar accidents like this? how often does he go in reverse in the middle of the road? not trying to offend, but did he pull a rice-reverse? the one where you reverse all fast, unsafely, and stupidly?