Years ago another contractor installed retina scan readers for access control at a local prison...
My first thought was "
You'd better prove to the residents that a freshly scooped eye won't work!
There was one place my dad used to work at. They had hand scanners for entry.
The security people casually noted that a severed hand wouldn't pass the scanner, because the size and shape of the hand would change due to being drained of blood.