Saucedo was charged with robbery, and presented an alibi defense. His counsel did not advise the prosecutor of his alibi witnesses until the trial had already started. The trial court permitted their testimony, but instructed the jury with CALJIC 2.28, which allowed the jury to consider the weight and significance of the late disclosure. The appellate court here found the instruction “problematic” because it encourages speculation and offers insufficient direction. However, they found its use here harmless because it was “merely a vehicle for credibility challenges that would have been made even in the absence of the instruction.” The prosecutor focused not on the delayed discovery, but on the late appearance of an alibi.