This summary is not the rule. The rule text controls.
Both sides in a criminal case have to keep sharing new evidence as it comes up, not just at the start. If the prosecutor or defense finds new evidence, or decides they want to use evidence they didn't plan to use before, they have to tell the court and the other side right away. This applies whether the discovery happens before the trial starts or even after the trial is already underway.
The point of this rule is to stop surprises in the courtroom. Neither side should be able to hide evidence and spring it on the other party at the last minute. If new evidence turns up, both sides need to know about it quickly so they have a fair chance to respond, ask questions, or prepare their case around it.
This rule keeps applying throughout the entire case. It doesn't end once the initial evidence has been shared. As long as the case is going on, whether that's the weeks before trial or during the trial itself, both sides must stay honest and upfront about any new evidence they find or plan to use.
