If you think you have to let murderers free because of democracy, you don't support democracy, you support murder.
An investigation ending in a jury trial is not, by any standard, despotic nor authoritarian.
However refusing to bring charges against someone in your same political class because they ran against you or might do so in the future absolutely is authoritarian and is the sign of an oligarchy wherein those with enough money are free from consequences.
Neither scotus nor the federal courts can bring charges, only oversee trials for said charges, or in the case of scotus, determine whether laws are constitutional and were followed during trial.*
Therefore the executive, as has always been it's role would have to bring charges.
Obviously courts can bring contempt charges, but only during and after a trial.