There’s also an episode of ER where Dr. Chen (IIRC) is found to have tell-tale stains on her sweater (IIRC). She’s so dignified and indignant about the snickering, pointing out all the other things it could be, that you feel guilty about snickering along with the characters. Then at the end she throws the sweater (IIRC) away with the most guilt-ridden and ashamed expression on her face you can imagine, putting the lie to her proclamations.
It was actually very touching. And hawt, because you know … Dr. Chen. Dirty hawt.
I agree with the suggestion that it is probably laundry detergent. You’d be surprised at how much organic stuff glows under UV/Black light; in fact, the fact that many things DO fluoresce is the basis for UV/Vis spectroscopy and the most common detectors for HPLC analyses. Entire fields of chemistry/entire analytical jobs rely upon the ability of things to glow under UV, down to the point of being able to tell different molecules apart based upon it!
My diamond from my engagement ring also fluoresces blue. Very pretty!
Just to add a data point, I’ll say: none of the black lights I’ve ever tried (four of them, from stores like Wal-Mart) have caused semen to visibly fluoresce at all. Lots of other stuff, including laundry detergent, but not semen. I always wondered if the CSI-types used some kind of special black light, or if it only glows very faintly and the purple glow from the light washes it out, or something.
The first time I ever heard of this forensics technique was in one of Patricia Cornwell’s Kay Scarpetta novels. In that one, the light had a special name, but I don’t remember it now. I’ll check tomorrow at work if nobody beats me to it.
I’m going to chime in here, as somebody who has been carrying around a UV-light keychain for the better part of a year: yes, it does, but so do a ton of other things, including:
Coca-Cola
white paper
some detergents
some antibacterial soaps
some Chap Stik
motor oil
antifreeze
bacteria scum in the sink
OK some real experimental data: I tested it and it didn’t glow under fluorescent black lights, either fresh or dried. However, I’d wager that the UV lights they presumably use for crime scenes probably utilize the more dangerous, cancer-causing UV wavelengths, which would be forbidden for general use in bars, etc, due to the fact that they easily cause sunburn, cataracts, and damage DNA.
Oh, and laundry detergents definitely glow very strongly.
Back in the eighties and nineties, when I sometimes found myself in blacklit situations where LSD was being used, I used to amuse myself by using a q-tip to apply cryptic symbols to my face in coffee. Dries invisible, and then later, under black light, you trip the hell out of your fellow heads.
