EDIT:
The law is complicated on this topic and it varies by region. I didn’t think this needed saying when I made the post, but this isnt an end all be all on the topic, it’s just something I found interesting & posted it to c/Today I Learned.
Don’t take legal advice from a Lemmy post. Talk to a lawyer.
The Purpose of Portable Breath Tests
Portable breath tests are commonly used by law enforcement officers to quickly estimate a person’s blood alcohol content (BAC) at the scene of a suspected DUI offense. These handheld devices are designed to provide immediate results, helping officers in their decision-making process during a traffic stop or investigation.
It is essential to understand that a portable breath test is different from the more accurate breathalyzer devices used at police stations or during formal chemical testing. While portable breath tests can provide an initial indication of a person’s intoxication level, they should not be considered as wholly accurate or infallible.
https://rhilllaw.com/blog/2021/03/can-a-portable-breath-test-be-used-in-court/
A related TIL is that none of these machines are built to detect blood alcohol levels. They detect any dissolved organic compound with a methyl group, most of which get absorbed into the blood orders of magnitude more easily than alcohol. Working with VOCs in an enclosed space without PPE can make you blow drunk on these. A good reason to demand a blood test when you know the machine is wrong.