§ 844 Jury may be discharged, when.

If a jury has already been picked and the case starts moving forward, a judge can still stop things and send the jury home under certain conditions. This happens when the court realizes it does not actually have the authority to handle the case. It can also happen if the charges, even if everything in them is true, don't actually describe a real crime under the law.

In plain terms, this rule gives the judge a way to end a case early if there's a basic legal problem with it. The judge doesn't need the jury to decide anything in these situations, because the case shouldn't be going to trial in the first place. This protects people from being tried on charges that don't hold up or in a court that doesn't have the right authority to judge them.