unreliable narrator

noun1

1. •
   A narrating character or storyteller in a story (such as a film, novel, play, or song) who provides conflicting, inaccurate, misleading, or otherwise questionable information to the audience or reader.

   • […] Patrick, for all his brutal truth telling, is an unreliable narrator. You see, he is mad—so mad, he probably committed the murders in his head. Which still makes him one sick yuppie. — 2000