Description of Two Wrongs Make a Right

Two Wrongs Make a Right is a fallacy in which a person "justifies" an action against a person by asserting that the person would do the same thing to him/her.
This sort of "reasoning" is fallacious because an action that is wrong is wrong even if another person would also do it.

Examples:
-Bill has borrowed Jane's expensive pen, but found he didn't return it. He tell's himself that it is okay to keep it, since she would have taken his.
- Jill is horrified by the way the state uses death penalty. Bill says that death penalty is fine, since those the state kill don't have anything against killing others.

In my opinion the first case is an example of two wrongs make a right as a fallacy. It is wrong even if the other person would do it. But in the second case it's a bit more complicated. It is a moral issue that the death penalty confronts, and there is probably no right answer. I believe that since murders don't have nothing against killing people they should not be able to say that they don't want it for them. This is my opinion. Now, what do YOU think?