I am just wondering when it is decided to use a physical FST instead of or in addition to a blood alcohol indicator? (or other scientific test) Aren't there instances where this test can be misleading or not applicable? Such as with people with certain medical conditions or physical disabilities that would make them unable to pass such a test at any point in time. Since the person's condition would not stop them from getting a driver's license and might not be indicated on their license, how would this situation be handled? Thank you for your response PS. I have not received a DUI and will never because I don't drive under the influence, just a question about relevance.