I'm sure most people have heard this myth at least once or twice, "Your hair and fingernails continue to grow, even after you are dead." This creepy myth, fortunately, is not true. I found a description of the myth on snopes.com Hair and nails both require living cells to grow, and so it is not possible for them to grow after a person has died. The reason they appear to be growing is because the body dehydrates after death. During dehydration, the skin around the nails and on the head shrivels and pulls back, making the nails and hair appear longer. However, they have remained the same length, it is the skin that has shrunk. This video explains all of that:
Using the scientific thinking principle Falsifiability, this theory can be proven wrong, as both of these things require living cells to grow. We can also look at this theory with Scientific Thinking Principle 1, Ruling out rival hypotheses. When looking at other possible explanations we can see that there is a better explanation for what's going on: the process of dehydration. Since this explanation can be proved and is a much simpler explanation(Occam's Razor) we can conclude that the theory that hair and nails continue to grow after death is not true.