A more thorough explanation:

A runaway grand jury is a type of grand jury that acts against the prosecution. A grand jury is a group of people, usually 23, who decide whether to issue indictments in ex parte proceedings. They sit permanently for at least a month and sometimes up to a year. If the grand jury decides that there is enough evidence to hold a suspect for trial, it returns a bill of indictment charging the suspect with a specific crime.

However, a runaway grand jury acts perversely by failing to return an indictment that the prosecution has requested. This means that the grand jury is essentially opposing the prosecution and not fulfilling its duty to evaluate evidence and issue indictments when necessary.

For example, if a prosecutor presents strong evidence to a grand jury that a suspect committed a crime, but the grand jury refuses to issue an indictment, it could be considered a runaway grand jury.

Overall, a runaway grand jury is a rare occurrence, but it can happen when the grand jury members have biases or are influenced by external factors.