The defendant was sentenced to 10 years in prison.

Literal

Defendant [topic-は] imprisonment-10-years [possessive-の] sentence [object-を] was-sentenced.

懲役10年の刑 means 'a sentence of 10 years imprisonment.' 懲役 (ちょうえき) is 'imprisonment with hard labor.' 宣告された is the passive: 'was sentenced.'