The narrator's emotional instability in Tell Tale Heart drives him to murder, showcasing clear signs of mental illness through obsessive behavior, hallucinations, and irrational actions.

• The reasons narrator tell tale heart insane include his fixation on the old man's eye, leading to murderous intent despite claiming to love him
• His emotional instability manifests through anxiety, hallucinations of heartbeats, and impulsive confessions
• The narrator's confidence and insanity is evident in his delusional belief of superior senses and lack of fear when police investigate
• Repetitive behavior and irrational thought patterns further demonstrate his deteriorating mental state
• His actions warrant treatment in a mental institution rather than capital punishment