Can I get food poisoning from eating Crisps 3 months past expiry date?

The date stamped on a package is the date the guarantee expires. It does not mean the food magically turns bad on that date. Crackers are made with shortening and the shortening will turn rancid if there is a hole in the package, even a small hole. If you ever get a rancid cracker, you won't want another one.

You could eat them three years past the expiry date and they would be fine. They are dehydrated potato. It does not spoil as long as the bag has not been punctured.

first of all, I would be willing to bet the word "expired" doesn't even appear on the label, does it?
Second, if they taste good, they are good.

they sure won't taste very good - you might just projectile vomit all over the house