Under what condition would the results from the Intoxilyzer 8000 be considered invalid?

The results from the Intoxilyzer 8000 would be considered invalid if the subject's oral cavity test exceeds acceptable limits, indicating contamination. This is significant because the purpose of the oral cavity test is to ensure that there is no residual mouth alcohol present that could artificially inflate the blood alcohol concentration (BAC) results. Excessive contamination can skew the measurement and lead to inaccurate results, as it may suggest that alcohol had been recently consumed or that the breath sample does not accurately represent the subject’s actual BAC.

While other conditions mentioned may impact the reliability of the results, they do not necessarily invalidate them in the strict sense. For instance, testing a subject who is underage or who has consumed alcohol shortly before the test could raise legal or ethical concerns, but it doesn't inherently affect the device's functionality or the accuracy of the measurement taken, unless other specific criteria are breached. Calibration discrepancies affect the performance of the device over time, but as long as routine checks and recalibrations are in place and the necessary maintenance is adhered to, this is typically managed within testing protocols. Thus, contamination is the key issue that directly invalidates the test results.