Fluctuations in layer height that are not visible? Dude, most printers are not even able to achieve a layer height consistency that would be invisible to the naked eye if they wanted to.

So when I turn on variable layer height this whole thing goes out the window. Or if I post process and sand the parts. Oh I know what if I use a slicer and firmware like klipper to bypass everything. No 3d printer that isn't locked down already by closed ecosystem will never have this "code" in the parts.

This has to be borderline useless as a positive identification tool, given that people can...

1. Make their own models
2. Run open source slicing software
3. Inspect their own gcode
4. Print from flashcard on a 100% offline printer with known clean firmware, such as the most common Ender 3.

How about they just focus on other methods of apprehending violent criminals and leave hobbyists alone.