Learn Turkish: Suçsuz adamı kim savunmalıydı? - Who should have defended the innocent man?

It combines the verb root savun (defend) with the necessity suffix -malı (should/must), a buffer letter y, and the past tense suffix -dı. When you add the past tense to -malı, it changes the meaning from a present obligation ("should defend") to an unfulfilled past obligation ("should have defended").

Why does the verb savunmalıydı not have a personal suffix at the very end?

Because the subject of the sentence is the question word kim (who). When kim acts as the subject of a sentence, the verb is conjugated in the third-person singular (he/she/it), which does not take a personal suffix.

Why is it adamı instead of just adam?

The suffix -ı is the accusative case marker, used for specific direct objects. The verb savunmak (to defend) requires the accusative case for the person or thing being defended. Since we are talking about a specific innocent man, adam becomes adamı.

How does the word suçsuz mean "innocent"?

It is made up of the noun suç (crime, guilt, or fault) and the suffix -suz, which means "without" or "-less". Literally, it translates to "guiltless".