[TheLML]

Modern fingerprint readers rely on the conductivity of your finger, so a cut off finger (or the finger of a dead person) can't per se unlock a phone.

[immad]

A dead persons skin is still conductive.

[Laforet]

There are better ways to detect whether the finger is still attached to a live person.

https://www.newscientist.com/article/mg21128225-100-fingerpr...

Nevertheless it probably won't ever be completely reliable short of installing a hypodermic needle with the sensor to take a blood sample every time :)

[war1025]

Was it GATTACA where the main character used a prosthetic thumb add-on to fool the blood check every day on his way in to work?

[djsumdog]

Yep, fake hair samples and fake blood patches under the skin. There was a lot of detail written into that movie.

[rhizome]

Andrew Niccol is so good!

[covercash]

And Demolition Man where he used an eyeball on a pen to fool the optical scanner.

[tracker1]

I changed it... illuminate... deluminate...

[djsumdog]

Well this escalated quickly.

[TheLML]

Yes, but only for a while.

[robin_reala]

The under-screen ones are ultrasonic as far as I’m aware.