Audrey is being held at gunpoint by Roger on a rooftop. Roger tells Sarah, Audrey's sister, that she must shoot and kill Steven. Sarah pleads with Roger to let her go and that she doesn't want to Kill Steven. Roger tells Sarah that unless she successfully shoots and kills Steven, he will kill Audrey. Roger has a violent reputation and Sarah has good reason to believe that Roger will follow through with his threat and commit murder if she doesn't comply.

Roger points out Steven to Sarah while he (Steven) is walking on the other side of the street. He (Roger) tells Sarah to take the shot. Sarah, fearing for her safety and her Sister's safety, takes careful aim at Steven, gauges the wind and change in elevation, and fires a precise shot penetrating Steven's heart. Steven dies as a result.

What crimes if any has Sarah committed? Are there any plausible defenses available? Be specific and explain your reasoning.