Are prosecutors free to choose not to prosecute particular cases?
Prosecutors may choose not to pursue a particular case or cases under the principle of prosecutorial discretion—the power to select which cases to pursue and which to settle. As a representative of the state, prosecutors decide whether it's in their "client's" interest (i.e., in society's interest) to seek a conviction in a given case. Their decisions are not generally subject to judicial review, as courts have affirmed.
In October 2020, as the Senate considered Amy Coney Barrett's Supreme Court nomination, 64 prosecutors pledged "not [to] prosecute women who obtain abortions and health care professionals who provide treatment," refusing "as prosecutors" to "criminalize healthcare decisions." Such blanket statements unrelated to an individual case are unusual. There are 2,300 prosecutors offices in the U.S.