This summary is not the rule. The rule text controls.
Once a party has shared information during the discovery process, they can't just stop there. If they later find new evidence or material that should have been handed over earlier, they have to speak up right away. This applies whether the new information turns up before the trial starts or even after it's already underway.
The party who finds this new evidence must tell the other side, or the other side's lawyer, or the court as soon as they know about it. They can't sit on the information or wait to see if it matters. The goal is to make sure both sides always have the full picture and no one gets blindsided by evidence that should have been shared sooner.
This rule connects to West Virginia's criminal procedure rules, which lay out the specific steps for how this notification should happen. In short, discovery isn't a one-time task that ends once the initial exchange of evidence is done. It keeps going throughout the case, and both sides have an ongoing responsibility to keep each other informed.