A mobile phone has been stolen. There are 3 suspects P, Q and R. They were questioned knowing that only one of them is guilty. Their responses are as follows : P : I did not steal. Q stole it. Q : R did not steal. I did not steal. R : I did not steal. I do not know who did it. Who stole the mobile phone ?

• P's statement consists of two parts: 'I did not steal' and 'Q stole it'. If P is guilty, both parts are false, which is consistent with the rule that the guilty person lies.

• Q's statement consists of 'R did not steal' and 'I did not steal'. If Q is guilty, the first part is true (R is innocent) and the second is false. This creates a mix of truth and lie, which is not explicitly ruled out for the guilty party in standard logic puzzles unless specified as 'always lies'.

• R's statement consists of 'I did not steal' and 'I do not know who did it'. If R is guilty, the first part is false. The second part is subjective; a guilty person might claim ignorance. This is also consistent with lying.

• Since the statements do not contain direct logical contradictions that eliminate two suspects definitively (e.g., if P said 'Q stole it' and Q said 'P stole it', we could deduce), and the truth-value pattern (True/False vs False/False) is not strictly defined for the innocent vs guilty in the problem text, multiple scenarios remain logically possible.

• Therefore, without additional constraints on the truthfulness of the innocent suspects (e.g., 'innocent always tells the truth'), the identity of the thief cannot be uniquely determined from the given statements alone.