Why was Mikhail Lermontov arrested and exiled to the Caucasus in 1837?

Mikhail Lermontov was arrested and exiled to the Caucasus in 1837 because of an elegy he wrote following the death of the poet Aleksandr Pushkin in a duel.1

In this poem, titled "Smert poeta" ("Death of a Poet"), Lermontov expressed the nation's grief while simultaneously denouncing not only the man who killed Pushkin but also the court aristocracy. He characterized the members of the court as the true culprits of the tragedy and as executioners of freedom. Once these verses reached the court of Nicholas I, the authorities responded by arresting Lermontov and ordering his exile to a regiment stationed in the Caucasus.12