Generally pardons are plenary powers, but individual state constitutions may vary. Typically, there is no need for a conviction (or even indictment) for a pardon to be issued. It's generally accepted that pardons can be issued any time after the commission (or alleged commission) of a crime, but can't be granted in advance.
“[Pardons] can’t be granted in advance [of a crime]”
Unless you are BLM / antifa. They generally have blanket amnesty from every Dem city in the country to go into full insurrection mode without any fear of consequences.