Yes, you can, unless the recipe specifically calls for fresh berries. For this recipe, fresh, in-season raspberries are the best option because they will give you the best flavour, and texture, AND result in better muffins, overall. However, frozen can be used instead if you don't have fresh. To use frozen raspberries, thaw them completely on a paper towel, and pat away all extra moisture (this is important because any extra moisture can alter the recipe). Gently fold them into the batter, don't over-mix or the berries will break down and the batter will turn pink.