Last August, Chief Judge Beryl A. Howell of the U.S. District Court for the District of Columbia empaneled a grand jury to hear evidence from the special counsel. That grand jury would not automatically terminate if Mueller and his team were fired. Legally, the individual U.S. citizens currently hearing evidence from Mueller’s investigation will remain a duly constituted grand jury until Howell discharges them. And Trump does not have the power to order Howell to do so.
In the event Mueller and his team were to be fired, Howell will have a big decision to make.
If she permits the grand jury to continue, she will hardly be acting without precedent. When America’s founders wrote the Constitution, and for 150 years thereafter, it was not uncommon for so-called runaway grand juries to go beyond the prosecutor’s “instructions” in issuing indictments. These runaway grand juries became virtually extinct after the 1930s, when a new law required a prosecutor’s signature before an indictment can be issued.