I work in a maximum security prison in Michigan.
The prisoners there work in the kitchens, and, make and serve the food that the other inmates, and, some staff that aren't too bright, eat.
Spitting, pissing, shitting, snotting, and, jerking off into the food is common.
One time, they found a turd floating in the coffee pot in the officer's dining room.
I opened up a large food service container of coffee a couple years back that was going to be served to inmates with the breakfast meal, and, almost puked all over, it smelled so bad of shit and piss.
Another time, an officer was eating chili in the officers dining room, and, found some crunchy things in it. He started picking them out of the chili, and, wiping them off, to find out what they were, and, he discovered that they were fingernail clippings.
Another time, at a place I worked, the inmates put oven cleaner in the offcer's coffeepot in the cellblock.
I read a letter once, from an inmate I knew, to another inmate I knew, and, he was bragging about digging the chocolate chips out of cookies he got with his tray, putting boogers in the holes, and, then plugging the chips back in, and, selling them to other inmates in the unit. He said he was going to put shit (feces) under the pepperoni in the pizza they were going to serve next week, and, sell that, too. Prison inmates have also been known to sell duplicating fluid or solvents as prison made booze to other inmates, which kills them, or makes them go blind.
As an officer, have I ever contaminated an inmates food? No. But, when I was working segregation (the hole) there were a couple of times when I handed a real asshole type inmate his tray, after picking it up off the side of the cart, and, saying, "Oh, this is your tray". Nothing was wrong with the tray at all, but, he had to wonder.
Hey, look on the bright side! Many of these guys will get out soon, come to a community near you, and, get fast food jobs.
"May I take your order"?