sometimes there is evidence on evidence, like fingerprints
whenever you collect a peice of evidence, it brings up a close up view of that item, and you can look for more evidence on it
there are quite a few items with more evidence on them, and some even have 2 things on them
but from what i recall, there are only 4 items with 2 things on them
- the keys from case 1
- the murder weapon from case 1
- the box of needles from case 3
- the jar lid from case 4
but there is a long list of things with at lest one peice of evidence on them (there are at least 5 per case) although some have more then others