He needs the help of a qualified marine accident attorney.
National and International law requires the right of way be given to the least maneuverable vessel. That is the basic accepted premise on which all laws of navigation are based, whether on land, in the air, or on water.
I was in a very similar situation in ‘87. I was hit while anchored at night. Long story made short, I prevailed.
Get a good attorney.
National and International law requires the right of way be given to the least maneuverable vessel.
First, that is not always the case. RULE 9, Narrow Channels. Huck Finn's raft, whether floating down the Mississippi or the Delaware; while less maneuverable, does not have the right of way.
Second, location matters. Not enough information in the story to make an educated guess. Where did the mishap take place? International, Inland, Western Rivers, or State waters. A whole string of 72 COLREGS Steering and Sailing Rules are in play with this incident. A good maritime attorney will know.
Given a loss of life occurred and a law enforcement agency is involved; the nearest USCG unit should be called to conduct an independent investigation.
Cheers,
OLA