I hear that some policemen may grab a folder, while it is closed, BY THE EXPOSED BLADE ONLY, then vigorously whip it. If the blade opens (or in this case if the handle "opens"), then they regard it a gravity knife. So be careful.

I wonder whether the best solution is to carry a fixed kitchen knife and carry it around wrapped in frilly tissue paper in a William & Sonoma bag.

Also, you cannot bring pepper spray into New York State. If you want something like that, you need to purchase locally. The merchant will have to record your name for the authorities. Only designated stores sell pepper spray.

Fortunately many parts of NYC are quite safe. But never lose your situation awareness no matter where you go.

Enjoy your trip!