Back in the day before DNA tests and mass spectrometers, it’s plausible that a vigilante could maintain a secret identity, especially if you have an environment where the bad guys have some weird unspoken rule about not unmasking them the instant they get knocked out, because otherwise why wouldn’t they? But with modern forensic science, it would basically be impossible. The first time a vigilante gets their lip split in a fight, the authorities would have their DNA. Swab it off someone’s knuckle, from under a fingernail, or a little spatter on a jacket or wall. Spit, skin cells, heck, just capturing them walking down a hall could be enough for gait analysis which could enormously narrow down a list of suspects.
Edit: I just wanted to add this since a few people are pointing it out; I know getting someone’s DNA doesn’t let you immediately identify them if you don’t already have a match on file, but it’s a slam dunk once you do get that match. And if they have a brother or uncle that’s a felon, then you’re suddenly a lot closer to knowing who you’re after. Plus, if you find the same DNA at 20 different scenes, then you have evidence that the same person was involved. Otherwise when you catch the guy, he could say “Oh I only was at the one scene you have evidence for, in fact I’m not even “Vigilante Mask” just a fan of his.”
In the case of someone like Batman, it can be argued that the cops kind of rely on him unofficially and don’t work too hard to unmask him. Also Bruce Wayne probably has the resources and contacts to have his DNA and fingerprints purged from any databases, but someone like Spider-Man? Unmasking him would probably be trivial if the authorities really wanted to.
The only way to avoid being identified would be to fight crime in one of those level 5 hazmat suits, or police the whole battle area in a super OCD manner for hairs and blood and bits of dirt you tracked in from your garden, recover all your Weasel-a-rangs, even the one that slid under the newpaper press or was deflected out the window by the ninja the bad guys hired to beat you in their desperation. Also you’d have to fight quietly and hope no one calls the cops on you for the noise so you have time to clean up. No stopping daylight robberies for you! Just brawls in abandoned warehouses.
Of course I can’t mention superheroes with OCD without linking OCD-Girl! Unfortunately it’s posted with some blogging front end and I can’t figure out how to view the comics at a legible resolution. If anyone does, post in the comments and I’ll put it up here, cause the comic is pretty funny.
Panel three obviously contains some other cameos. Usually if they’re from regular “big” media sources, I like to leave it up to you guys to root them out, cause it’s fun being the person who recognized the obscure thing, but these cameos are small or single team web projects, so I’ll link them here.
The two guys on the top row are just randos I made up for that panel, but many of you should recognize Spinnerette there in the middle. If you haven’t ever checked it out it’s a well drawn and funny webcomic.
On the bottom row is the “Ask a Ninja” guy which was a very funny but unfortunately short lived youtube series… though checking the channel just now I see he’s still slowly updating, or at least remastering his old videos, so… I guess I know what I’m catching up on during lunch.
Next to him is not Carmen San Diego believe it or not, it’s Ronni Kane from another webcomic called Giant Girl Adventures. Guess what her power is?
Weird having only one person in the Who’s Who after a possibly record breaking one on the previous page.