Now I've got 6 books out there with 6 more on the way. And people are still really helpful. I just got done talking to a woman in a toxicology lab. She'd never heard of me before. I just called her up out of the blue. But she walked me through exactly how they screen blood from an autopsy for chemicals. Like they buy "production loss blood" from the Red Cross (expired blood, I guess), and they buy "liquid controls" from drug companies (not in enough of a quantity to be considered a controlled substance), and they add the liquid control to the production loss blood and test it so they can see what the blood with a given substance will look like on the test machine.
Also, they screen blood on a urine screen machine, after taking out all the cellular debris - red blood cells, white blood cells, and platelets. What do I know? That sounds like everything that is in blood.
Anyway, it's fun to learn new things - especially when they help your plot.