Okay, no leather shoes for Yom Kippur (or Tisha B'Av). I always assumed if the label said
ALL MAN MADE MATERIALS or
100% CANVAS or something like that, that we could trust the label. (Would they really sneak leather in? It's more expensive, right?)
What is the Halachic standard for how certain I need to be that a pair of shoes is actually leather-free, particularly with today's complex market for manufactured shoes? Is there Halachic literature on this, or can you report any verbal response you've received on it?