If the possibility of a psycho in your building makes you nervous, you're probably better off not taking "free candy", and just avoid the stress. (Much like I decided I would rather do half a dozen very cautious measures, than get food poisoning even once.)

For what I put on the free shelves, it's things nearing/at the best-by date, the year and month of that are usually marked prominently in handwritten Sharpie on the front of the package, and I don't put things there if they have any risky signs.

For example, recently, a packet of instant potatoes was nearing best-by date, but the packet seemed puffed up more than usual, like I think I would've noticed when I bought it. So I erred on the side of caution in throwing it away, rather than risk a neighbor, maybe unaware of the suspiciousness, getting sick.

What's toxic food and how do you make it? That's the point of this thread...