Of course I can, but it would be a very lengthy and complex discussion.  In a nutshell, Virginia DUI / DWI law can be separated into two categories:  (1) cases involving impairment of the driver and (2) cases which have nothing to do with impairment of the driver. 

Virginia DUI / DWI cases involving impairment of the driver:  These cases are sometimes referred to as "common law" DUI cases.  Virginia DUI law makes it illegal to: 

• Drive while under the influence of alcohol.  
• Drive while under the influence of drugs to a degree that it impairs your ability to operate a motor vehicle safely.  

NOTE:  Successful prosecution of these cases does not require any proof of the amount of alcohol or drugs in the driver's body.  This is the law under which DUI / DWI offenses are prosecuted when there is no breath or blood test to rely upon. 

Virginia DUI / DWI cases which have nothing to do with impairment of the driver:    These cases are sometimes referred to as "per se" cases because the proof of the violation is a measurement.  Virginia DUI law makes it illegal to:  

• Drive with a prohibited amount of alcohol in your system. 
• Drive with a prohibited amount of specific drugs in your system. 

NOTE:  Successful prosecution of these cases does not require any proof that the driver was impaired by alcohol or drugs.  The violation is simply driving with the prohibited amount of alcohol or drugs in your body.