As one example of what is considered reasonable suspicion, if I am a police officer and I am patrolling a high-crime area, and someone sees my police cruiser and runs away, that is "reasonable suspicion".
I am allowed at that point to chase and then frisk the person once I have caught them. Any evidence found at that point will stand up in court. I suppose with the Virginia law at this point I can detain the suspect while I confirm with the feds whether they are an illegal alien with a felony conviction.
If they do not run away and I instead speak with them and ask them questions--if their answers are inconsistent or they "keep changing their story" (as many criminals seem to do...perhaps not bright enough to keep a consistent lie going??), that is also reasonable suspicion and I can frisk them.
Thanks for the insight -
Unfortunately, "reasonable suspicion" might also include saying "no" if a cop asks if he can search your car -