Fruit – Can jam be made from frozen berries

From the comments, Henrik noted that there is a parasite in Sweden (called "Dvärgbandmask" in Swedish) that contaminates wild fruit. This is a type of tapeworm called "Echinococcus" in English. Its eggs can cause a parasitic disease called Echinococcosis or hydatid disease. According to this article, freezing the eggs to very low temperatures and/or freezing the eggs very rapidly is fatal to them. Given that modern "IQF" freezing methods for berries bring the fruit very quickly to below -20°C, I'd say that the danger from echinococcosis is very low (much lower than eating unwashed fresh fruit).

As for risks from bacteria, these are also very low because the process of preparing the fruit for freezing and then subsequently freezing them kills the majority of any present bacteria.

Store them unwashed. Take out any "bad" ones. I've had decent luck adding some paper towels to wick away extra moisture that seems to speed up the spoilage. Martha Stewart suggest going even further and spreading them out on paper towels on a sheet pan. I have no idea who keeps a fridge empty enough that they can store full sheet pans in there, though.

I've never tried this, but someone suggests washing it lightly in vinegar/water. *shrug*

Then of course, wash and freeze them spread out on a sheet pan (to make it easier to separate later). I assume this isn't what you want to do, but it is very effective, depending on how you plan to use them.