## 46. Who is Murdoch?

- A spy named Murdoch has infiltrated the country. He was arrested along with two indigenous residents (we will denote the defendants with Latin letters $A, B$, and $C$). One of the indigenous residents, mistakenly arrested along with the spy, was a knight, and the other was a liar. Of the three, only the spy was called Murdoch. At the trial, the defendants gave the following testimonies:

A. My name is Murdoch.

B. That is true.

C. Murdoch is me.

Who among the three is the spy?
46. Who is Murdoch? Since $A$ claims that he is a spy, $A$ is either a liar or a spy. Similarly, since $C$ claims that he is a spy, $C$ is either a liar or a spy. Therefore, out of the two defendants $A$ and $C$, one is a liar and the other is a spy. Thus, $B$ is a knight and gave truthful testimony in court: $A$ is the spy.