Case 1, image 1: This 36 year old man was shot in the chest through his black T-shirt.

Case 1, image 2: A careful look revealed black material consistent with clothing fibers, and NOT consistent with soot.

A forensic pathologist often takes a section of the skin around a gunshot wound to demonstrate the presence of soot and unburned gunpowder particles.

Beware, however, not all darkly pigmented material seen within the epidermis or dermis is soot. You must consider clothing fibers (if shot through clothing), tattoo pigment (if shot through a tattoo), disrupted hair shafts, bullet wipe, and other bits of debris that penetrated the skin. The best way to learn is to take a section of all gunshot entrance wounds so you can train your eye.

It is pretty difficult to see the characteristics of soot versus tattoo pigment vs clothing fibers in an image. You generally need to focus up and down to appreciate the three-dimensionality of these depositions.