It doesn't make any difference what you call it (sweater, jacket, coat, etc.) -- there is only ONE item of clothing under discussion. That one item of clothing is the outerwear Patsy wore to the White's dinner party. It was red and black and fibers consistent with the garment were found at the crime scene.
But "consistent with" does not equate with "match", so the fiber evidence is weak. Besides, there was a black and red scarf on the counter in the kitchen, and the scarf fibers could have been the source of the fibers at the crime scene. For instance, the scarf could have been the padding needed to properly use the ligature wrapped around JonBenet's neck as an erotic asphyxiation device.
And the fibers were microscopic, which often means they can float in the air and settle almost anywhere. Incidentally, there were hundreds of different fibers on the sticky side of the duct tape, not just four -- so the tape itself had likely been all over the place prior to being placed on JonBenet's mouth.
The fiber evidence shouldn't be discarded, but it is very weak evidence to draw conclusions from.
BlueCrab