He’s an actor, not a trained safety specialist. As far as I know, he’s not an avid gun handler in real life. How often did AB encounter, and have to recognize, LIVE rounds in the firearms he used on previous movie sets? In this case, live rounds were not recognized by the armourer, nor the AD.
He's a member of Actors Equity Union or he wouldn't be working on big movies. They have standards and protocols, one of which is that there should be a safety meeting with the actors there on the morning of any shoot that will be using prop guns or any other kind of gun. The protocol mirrors almost exactly what the Propmasters' Union protocol says.
A main piece of the protocol is that the actor is supposed to receive the gun from an armorer or safety specialist, who has performed a thorough check of the gun in the actor's presence and the actor is supposed to perform the same check of the chambers (for safety's sake and in order to follow the ordinary rules of gun handling).
So, we shall see what a jury says about all this after the experts testify.
Furthermore, someone was in charge of hiring the various unsafe persons on this set, and it sure looks to me like Alec Baldwin is one of them. That too will need to be heard in the future legal battle, as there is no account given to MSM about who hired and short-staffed the armory segment of props (we only know that some very experienced armorer said he wouldn't do the job without two full time assistants, was refused, and so he therefore turned down the job). The AD had been fired from a previous set for improper handling of gun safety issues, and a gun that ought not to have fired on the set of Rust had already fired 3 times, which was one reason that workers were walking out.
One member of the crew shot herself in the foot with a blank. That ought not to have happened. Who was that person? Not the armorer, so why did she have a gun in her hand? Guns should be locked up when not in use in a scene and only 3 people should handle the gun (armorer, AD and actor).