If a surgeon was handed the wrong tool or it was sterilized or whatever, then whoever hired the people who were assisting would have liability.
Two of the 5 production companies in this debacle go right back to Alec Baldwin; 3 others are tiny, independent filmmakers who just wanted their name on this production and probably ponied up some funds.
Who, in fact, was the producer who hired HG and the AD?
And if it's true, as her wikipedia says, Halyna was an activist and was organizing the strike about working conditions on the set, how convenient that she ends up dead. Since her husband is employed by one of the West Coast's most powerful law firms, a firm that specializes in liability and financial instruments for very large corporations (with worldwide branches), he certainly has a good pool of attorneys to counsel him on whether there could be something other than a wrongful death suit in this case. One of the crew has already hired an attorney and looks to be aiming at an intentional infliction of emotional distress suit. If it's true that this fiasco is covered by a mere $6M in liability, and that at least 2 of the production companies who owned this mess have deeper pockets than the others, it would not be unheard of for the producers to be sued for various torts. Even if the suits eventually fail, those production companies may have long months or years in court - and it will be expensive.