Alice: I didn't do it if and only if Derek didn't do it.
Bob: Alice did do it if I didn't do it.
Cindy: If I did it and Alice didn't do it, Derek didn't do it.
Derek: I didn't do it or Bob did do it, or Cindy did it.
Evelyn: I did it.
It is known for a fact that ONLY one of them did do it. If only one person told the truth, who did it? And who told the truth?