By not disclosing it to the defense. The only way for Nifong to avoid disclosing it in discovery is if he doesn't have it in his possession, and the only way to not have it in his possession is to tell the investigator or his supervisor not to give it to him, whether he says it directly or implies it indirectly through another person or through deed. These facts revealed in these reports are far too important for an investigator to make the decision to not include them as a matter of his own discretion.
Oh, okay. So Nifong doesn't WANT reports and then he doesn't have to turn them over to the defense.