Inspector arrested three persons- Kalia, Raza, Shera - on suspicion, in a theft case. It was found the one among these three was the thief. During the interrogation their replies were as follows.

Kalia: I am not the thief. Raza is the thief.
Raza: I am not the thief. Either Kalia or Sh era is the thief.
Shera: I am not the thief. Raza is not the thief.

If exactly one person among them always speaks the truth, another always speaks lies and the third alternates
between the truth and lies, then who is the thief?