The key is deep frying under pressure, some considerable time after the murder, no doubt though hopefully not long before disposal of their corpses via a hybrid mechanical & chemical process so horrific that it must surely be illegal under international law.
Is this another query about cyanide? Only I think I read you mention being Swedish & this issue has come up a few times always from a Swede, all iirc which is unlikely.
If that is your concern, keep an eye on the following thread as James mentions he’ll be linking to an article on this subject: Ground flaxseed and cyanide