system
Given the following post, respond as if you're commenting on Reddit:
human
Why do police still use sobriety tests when more objective and accurate breath testing machines are available?
gpt
Police officer here: 

There is a lot of speculation in this thread that is incorrect when applied to US law. The reason is twofold. 

One, a breathalyzer does not show impairment, only the level of alcohol in your blood. However, you are being arrested first and foremost for driving impaired. In court, the primary argument being made is that it was unsafe for this person to be driving. You can still get a DUI and be under 0.08.

Two, you cannot legally force someone to blow in a breathalyzer. You have to arrest them first for driving under the influence. 

The standardized field sobriety tests are very accurate at determining when someone is above 0.1 when performed by people have been trained in them. NHTSA has performed many large scale field trials validating them.