The legal standard for indictment involves a reference to ability to prove the case beyond a reasonable doubt.
Not that the legal standard means spit, just that it exists and it does contain that reference.
ABA Criminal Justice Standard
Standard 3-4.3 Minimum Requirements for Filing and Maintaining Criminal Charges
(a) A prosecutor should seek or file criminal charges only if the prosecutor reasonably believes that the charges are supported by probable cause, that admissible evidence will be sufficient to support conviction beyond a reasonable doubt, and that the decision to charge is in the interests of justice.
Like most else in the practice of law, this is total bullshit ruse, meant to give the people faith and confidence that the rigged system is not rigged.