I think you're right - HGR comes out as the villain in this (and the Judge ruled that Alec's role as producer in hiring her cannot be introduced via expert witness at a pre-trial motions hearing).
However, it's a bit like other deaths related to negligence, more than one person may be involved in a chain of bad decisions. It's still true that Baldwin did not go to the safety training (his defense did not dispute that - I think they might still try, though). It's still true that the
SAG and other union rules require a 3 part check to a gun - the last one by the actor in the presence of the AD (which didn't happen here).
If even one juror believes that HGR is the true culprit and that the SAG/union/OSHA rules are all irrelevant in a criminal trial, then Baldwin will not be convicted. But it is Santa Fe. Santa Fe has the highest proportion of Ph.D.'s in science in the nation, per capita (because of Los Alamos and other reasons). Santa Fe County is very small. People are not happy that there's a trial in the first place (expensive). The rules of gun safety are known to every long time adult New Mexican, probably because it has a high rate of gun-related homicide and manslaughter - and a lot of it is negligence (kids finding guns, people brandishing and shooting in the air on holidays; when I lived there, I found it terrifying and we even chose where we lived to try and be out of areas where the holiday gun shooting occurred; we still had a child dead in our neighborhood due to a neighbor's negligence - neighbor was an elderly man who asked boys to feed his dog by going into his garage, there was a loaded gun somewhere in the garage).
I think that gun safety is one of the hottest political topics in contemporary New Mexico:
7th highest rate of death by gun in the USA, as I understand it from that link. People are quite concerned about the rising rate (and that includes manslaughter, and not just felony murder).
IMO