To understand why a second breathalyzer test is conducted on a novice driver with a rate of 0.20 milligrams per liter, it is important to consider several aspects:

- **Breathalyzer test:** When a traffic officer detects that a person has consumed alcohol, either because the initial test is positive or because the person shows signs of having drunk, a second test is conducted. This second test is done to **confirm the results** and ensure the accuracy of the initial measurement.

- **Permitted blood alcohol level:** For novice drivers, that is, those who have obtained their driving license less than two years ago, the permitted alcohol level is **0.15 milligrams per liter of air**. Since 0.20 milligrams per liter exceeds this limit, it is necessary to conduct a second test to verify and contrast the result.

- **Importance of the second test:** The second test provides a **greater guarantee** that the result is correct and helps to avoid errors in the initial measurement. This is crucial for making fair and accurate decisions regarding sanctions or measures to be taken.

In summary, the second breathalyzer test is conducted to ensure the accuracy of the initial result and confirm that the novice driver has exceeded the permitted limit, thus guaranteeing a fair and reliable process.