You can't be forced to give your password (self-incrimination), but, depending on the jurisdiction, the police can force your finger on the unlock screen.

The technology is a bit hush-hush, but it is already possible to read brainwaves, and "interrogate" someone through fMRI. Just thinking about your password may reveal it, if they are allowed to force your brain near a reader.

The first serious (public) ventures into this technology was around 2000. Advances in machine learning then made it possible to read objects and concepts that were not in a training set. It was used and tested extensively in Guantanamo Bay. The legal status is still ambiguous, but I guess that it is used just in very special cases (where the detainment itself may be legally ambiguous, such as at a black site).

The Legality of the Use of Psychiatric Neuroimaging in Intelligence Interrogation (2005) https://pdfs.semanticscholar.org/906b/8afdd39ecda3a265987a09... [pdf]

I think this is a great analogy and easy for the layman to understand.

I agree. BUT - the response will be: “well even if we wanted to, we don’t have the technology to read his brain. we DO have the technology to read his phone, but you nerds are keeping it from us.”

(Disclaimer: I don’t agree with this position but I have a lot of friends who think the government can do no wrong)

And if we had the technology to read the brain we would demand to read everyones brain 24/7

It's not a perfect analogy. The problem with the "back door" is that these keys will leak. They always do. It's a big danger to have a weakness in all our devices that we know, eventually, Russia, China, or Iran will get their hands on.