What's the legal limit in Virginia?
In Virginia the legal limit is 0.08.
Yes, you can be convicted of DUI in Virginia even if you blow below the legal limit.
The phrase "legal limit" is misleading because it doesn't mean that you're automatically guilty if you blow above it or innocent if you blow below it. The legal limit in Virginia, 0.08, just means that if you blow a 0.08 it's presumed that you're too drunk to drive. If you blow below the legal limit you can still be convicted of DUI, but the prosecutor will have a much more difficult time proving the case because they can't argue to the judge that you're presumed to be too drunk to drive. The prosecutor will have to rely on the field sobriety tests or other evidence to convict you.
What if I blow way below the legal limit? 0.05 or 0.04?
If you blow a 0.05 or 0.04, there's a presumption that you're not too drunk to drive. That means that the prosecutor will have to totally rely on other evidence to convict you and the other evidence must be extremely strong. They can't just say that you couldn't stand on one foot for 30 seconds. They will have to come up with significant other evidence in order for you to be found guilty. The only situation where I've seen a person who blew a 0.0 or 0.04 convicted of DUI is when medication or illegal drugs were also found in the person's system.
Can I be convicted if I don't even provide any breath sample?
Yes. You can be convicted just based on your statement to the officer, your performance on the field sobriety tests and your appearance and demeanor. That means it's important to remember you can refuse to participate in field sobriety tests and you can refuse to make statements to the police officer.