Generally, the consumer needs to demonstrate (prove) the goods were faulty at the time of sale. This is so if the consumer chooses to request an immediate refund or compensation (damages). It is also the case for any product returned more than six months after the date of the sale.
There is one exception. This is when a consumer returns goods in the first six months from the date of the sale, and requests a repair or replacement or, thereafter, a partial or full refund. In that case, the consumer does not have to prove the goods were faulty at the time of the sale. It is assumed that they were.
If the retailer does not agree, it is for him to prove that the goods were satisfactory at the time of sale.