Crackers that have remained sealed in the packaged are good for around to 9 months after the expiration date on the crackers.
So you can safely eat the expired crackers as long as they have not been expired longer than 6 to 9 months.
When crackers have gone bad they will usually start smelling bad so if you notice a bad vinegar like smell to the crackers or they taste bad then throw the stale crackers out.
It's unlikely you would get sick from eating the bad crackers but it's not worth the risk and your stomach will ache as a result of eating bad crackers.
So while you might not get deathly sick from eating the stale crackers you still will get sick from them and have a stomach ache.