Is it the customers or shop keeper's responsibility to check if a product is safe?

Both. The shopkeeper can get in trouble with the County food inspectors (in the US) for selling expired food (particularly perishables and dairy products, which spoil).

But the consumer (your cousin) should be self-aware enough to look at the date herself. You cousin bears at least half the blame.

If you want to make a big stink about it, you could ask the city/county food inspectors to visit the shop and do an inspection. The shopkeeper could get in trouble for selling spoiled food. The downside, of course, is that your cousin will never be welcome there again.

Liability is the responsibility of the shopkeeper. The customer enters into, essentially, a “good faith” agreement with the retailer, trusting them to provide safe foodstuffs. If the customer is, for example, European, and doesn’t understand that Americans numerically designate dates differently, it is not incumbent on them to know that.

The shopkeeper was trying to intimidate your cousin by denying blame.

If the shop is part of a national organization contact their customer service group and tell them what happened including the shop keeper’s attempt to put-off your cousin.
State or local food safety (government) should be contacted too. The government will remove all out of date food products, at least in my state. They have gone for normal inspections and emptied all out of date or non-dated food items from walk-in refrigerators into a dumpster.

I’m puzzled by the idea of “a milkshake” being out of date. Where I come from, milkshakes are made at the time of purchase, from fresh ingredients. I take it that this was some kind of packaged milkshake, which I’ve never seen before.

“In general” responsible store owners and managers check the expiration dates of perishable products and remove them from sales displays when the date has passed. But it’s certainly conceivable that in a large store, for example, or with new or overworked staff (or product mistakenly replaced in a wrong area, for example) that some goods can be sold that shouldn’t be.

The ultimate responsibility certainly rests with the consumer – always.

For one thing, with the example that you cite, unless your cousin returns the the store very soon after the incident, with the product in hand – and the receipt that shows that it was purchased recently – then how will the store owner know that it’s his fault, and not someone just trying to replace a product that sat on his own refrigerator shelf at home for a week or longer?

I’ve never seen or met a store manager who, presented with that evidence of a bad act on his part, wouldn’t take every reasonable measure to satisfy the customer and change his processes to ensure that it doesn’t happen again.

Yes my cousin returned with the product and yes it was packaged, and no she had no receipt; it is a small shop that does not give out receipts.

On average, only two people work at the store.

Sounds like a trip by the Consumer Affairs and Food Safety might fix the issue at the shop for future trips by your cousin
.

When I was in Jr High you could actually get what some could consider a milkshake in the school cafeteria. I would call it more of a malt in sealed contained that was probably shipped across the country.

But I think the thing here is a expectation of longevity. It is reasonable to expect that something consumed a few days after you leave the store shouldn’t make you sick as long as it is properly stored. It is bullshit that if I buy a block of mozzarella to make manicotti the night of purchase that I would need to check the date. After a few days it is on me.

My cousin drank some of the milkshake the moment she came home before throwing up.

Consumers innocently expect retailers to check that all products are in date. The retailers expect distributors who restock shelves to remove out-of-date products, and move the older “use by” date products to the front and put fresher products in the back. All three parties can be at fault if not focused on consumption safety.

Other factors to take into consideration: a sell-by date is not the same as an expiration date; the packacing might have been slightly damaged, thus causing contanimation.

One final thought: food poisoning doesn’t occur that quickly, does it? The cousin’s illness may have been caused by some other factor.

It was the taste of the dodgy milkshake that caused her to throw up, and other members nearly threw up just from smelling it.

It is a small shop with two people which means it is easy for them to keep track of what is out of date and what is not. I understand if it was an item that only expired or ran out of date but this item was 8 days pass that date and still on the shelf.

Both, someone should check if it’s expired but mostly the shop owner it’s his responsibility to clear out the shelves of old expired stuff.

Having never worked in a shop that only had two employees, is it common that they are trained and have the time to check expiration dates of all products?