It says in the epipen literature that the use of the pen is never contraindicated in an emergency. That should satisfy the lawyers.
In an obvious life or death scene, not using it will definitely cause harm, using it may or may not, so you go with the safest path.
Yes, it is odd that the mom did not know much about severe allergies.
www.foodallergy.org
Yes, it's not contraindicated, but that has nothing to do with the expiration date. If you think that's going to satisfy a trial lawyer, maybe you haven't observed many medical malpractice trials.
Unfortunately, EMS will not administer an expired medication. I suppose they could do it that one time and then start looking for a new job in another field, because they will lose their certification.
I personally agree with using an expired EpiPen in an emergency situation. If I'm staffing an ambulance, I won't do it -- but I wouldn't advise the parent not to.
There's at least one study out there that concluded that the "epinephrine bioavailability" of an outdated EpiPen is "significantly reduced," but it's still better than nothing as long it's not discolored.