How are ways to test for LSD in your system?

The only way I've heard it tested for (and I believe is a rumor) is a spinal tap.

I do not believe this as a single hit of acid these days is 200 micrograms of LSD, such a small amount that it's basically impossible to test for in any manner that I'm aware of.

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It's supposedly possible to test for it in urine, but the detection window is 12 hours so you almost have to grab the guy DURING his trip to get a positive.