Its a tough one to proove- and tech. a hard law to enforce- failure to allow a merge???? or the simplicity of being a prick driver? The only way he would be held accountable is if was high or drunk- and the tests were done at the time of the accident or if he was not following his companies regulations, such as driving too long without sleep. More likely then not he's just going to have to live with the knowledge that he ended a young womans life due to sheer ego. Rest assured, though you may never see it personally- karma will win out in the end... it always does.