Now that a grand jury has indicted Alec Baldwin on a charge of involuntary manslaughter for the fatal shooting of a cinematographer on the set of the film “Rust” in New Mexico in 2021, the contours of the looming legal battle are coming into focus. If the case reaches trial, the challenge prosecutors face will be convincing a jury that Baldwin was guilty of either the negligent use of a firearm or of acting with “total disregard or indifference for the safety of others” — even though investigato