All (most?) doctors [like me] are well aware that the expiry date for most drugs is notional rather than real. If I or my family get sick I use expired drugs that I have, or have scrounged from the pharmacy.
Not just doctors, the government as well. Our military stockpiles drugs and medication for emergencies, and keeps stuff for a minimum of ten years, often longer. They run extensive tests on it and it's still at 95-100% effectiveness after that time.
Yes, these results are public somewhere. (I forgot where I read them.)
There are a _few_ cases where something went wrong with some of them. And there were studies of public "drug went bad" stories in media. One woman did have kidney damage from Tetracycline (I think), exposed and stored in a damp environment. So even the cases where something happened, the situation was an outlier.
Older drugs are quite safe for the most part and it's hard to pin down reasons why they are not. There COULD be a small risk, but probably isn't. I still wouldn't store medications in a hot car, a pocket, purse, or backpack, or in a garage. But any house or office would be fine and low risk to use after the expiration date.