Question: I saw this question somewhere in the Internet(I forgot the source) and I think this forum is a good place to ask it.

According to what I know, the atoms in a persons body are replaced every certain amount of years:
<https://skeptics.stackexchange.com/questions/18427/are-all-the-atoms-in-our-bodies-replaced-on-a-regular-basis>

Then, if a persons body atoms are replaced every x years, should the person be prosecuted today for a crime that he/she committed x years ago, when today that person is physically another person(different atoms)? 

And lets say hypothetically that 0.00001% of atoms are never replaced, should 0.99999% of the sentence in years be eliminated (the person is 0.00001% responsible for the crime) ?

This is a related question in the forum:
[Am I still the same person as I was yesterday?](https://philosophy.stackexchange.com/questions/2747/am-i-still-the-same-person-as-i-was-yesterday)

Answer: 
Atoms do not contain little tags that say "I am part of user63152", and whose unique properties determine the actions of user63152. Indeed, aside from differences in isotopes, and a handful of observables like nuclear spin, atoms of the same type are indistinguishable from each other.

Thus, we needn't care whether the atoms are replaced every minute, every decade, or never. That ongoing entity which is you is you by virtue of emergent properties (like thought) which are robust to changes in which atoms you are made from. So while time may have *some* bearing on how we choose to prosecute crime, it should *not* be because there has been some swapping around of functionally equivalent parts.
It seems to me that this is just a reformulation of Theseus' paradox. Plutarch notes in his biography of Theseus that the ship that Theseus and the other Athenian youths returned upon was preserved by the city of Athens through the ages. As various planks and rails rotted, they were replaced leading to the question commonly discussed among philosophers over whether or not the ship we have now is one and the same as the ship that Theseus returned to Athens upon.

Really the question at hand is the very question of identity. It's not an easy question to answer. A good starting place is the subtopic Understanding the Persistence Question over at the Stanford Encyclopedia of Philosophy in the Identity entry: <http://plato.stanford.edu/entries/identity-personal/#UndPerQue>