Investigators are not allowed to blatantly ask any source about any issue - i.e. Tell me about his DUI arrest? Tell me about the his mental health counseling? The source has to bring up the topic. So, I have to ask if the person getting the clearance has ever been arrested…if the source says no (even though I know the person knows that the subject was arrested because the subject told me the source knows), I move on. Now, there are many times sources bring up topics and then they can be discussed. For example, at the end of the interview we always ask if there is anything else we should know? For example, I have had source bring up a person’s sexuality as something that could be used against the subject as blackmail…then we have to discuss the topic because they brought it up. So, if at the end of the interview, a person brought up the HIV+ status as something else we should know, or maybe it was brought up (by the source) as something that could be used against the subject as blackmail or coercion.
The only caveat to this entire thing is if there is an open public record that states the source would know about the information. For example, if the source was with the subject when he was arrested for DUI and the (public) court record stays the source was present…then we can ask about the specific arrest. But I don’t see how that would be the case in your circumstance.