Here's a request for an opinion on how I should construct the basic idea of magical forensics.
Pretty much the only magical forensic tool we've seen is the spell (charm?) Prior Incantato. Crouch uses this (in GoF) to make Harry's wand reveal the last spell it performed. (Usefull spell, that. I wonder if it still works if the wand has been broken?)
It is implied multiple times that spells interact with whatever they happen to hit, and occasionally what they pass on the way to their target. A mis-directed Stunning spell isn't too good on robes (OotP--a DA member sets someone's sleeve on fire, iirc), and a mis-directed Killing Curse can break statuary (OotP). I'm claiming this as canonical evidence of the possibility that spells leave a residue where they are used.
This is even more strongly implied in HBP, when Dumbledore and Harry vist the cave. Dumbledore can feel (and he may be using spells to reveal/track) trace magic in the area. Now, some of what he uncovers are active spells--protective wards, things related to the Inferi in the lake, etc. But this would seem to indicate the existence of magical "trace," and the ability of wizards to uncover and identify such trace.
My minor dilemma is this:
What should I focus on while developing the magical forensic tools for my wizarding CSIs?
From canon, I'm thinking very specific charms would be the most likely type of magic to use. Potions, maybe, especially for analytic work? Or maybe a combination, like the luminol+Alternate Light Source that the CSIs use to check for blood (potion + spell)?
I'd also like to know which you think would be more likely:
That magic could detect various differences in spell residue, to identify not only the type of spell but the wand (or wizard?) that generated it (grooves and striations on a bullet matching to the gun, for an analogy)...
Or that there may be magical analogues to actual CSI tools, used to gather things like blood and DNA and track the locations/actions of suspects through the scene that way?
I imagined, initially, that both might be true--but in keeping with the cultural emphasis on magic as the most important thing, I figured that magical forensics would be more developed, and the Muggle-based stuff less so (and less readily used).
Anyone who gives me ideas or really good thoughts will, of course, be acknowledged in the finished story. :-)