What kind of confirmation is essential if a high BAC is detected?

The correct choice, confirmatory test, is essential when a high Blood Alcohol Concentration (BAC) is detected to ensure the accuracy and reliability of the initial test results. The primary reason is that the Intoxilyzer 9000, like any breath alcohol testing device, can yield false positives or inaccurate readings due to a variety of factors, including environmental influences or user error.

A confirmatory test typically involves using a different method, such as a blood test or a second breath test, to verify the results obtained from the initial screening. This additional testing helps to confirm the presence and level of alcohol in the individual's system, providing more robust evidence for legal and administrative actions that may follow.

While visual confirmation, informal witness confirmation, and subject's confirmation might provide context or support, they do not serve the same purpose as a scientifically reliable confirmatory test. Only objective testing methods can substantiate high BAC claims in a manner that meets legal standards.