Learn German: Ist der Verdächtige schon verhört worden? - Has the suspect already been interrogated?

When building the passive voice in the Perfekt tense, German uses worden as the past participle of the helper verb werden. You only use geworden when werden is the main verb of the sentence, like in Er ist alt geworden (He has grown old). Because this sentence is passive, the ge- is dropped.

Since the English translation says "Has", why does the German sentence start with Ist instead of Hat?

In English, the passive perfect uses "to have" (as in "has been"). In German, the passive perfect always uses sein (to be) as the conjugated helping verb. Since der Verdächtige is a singular third-person subject, we use Ist.

Why are there two verbs at the very end of the sentence, and why in that order?

In the Perfekt passive, you need two past participles: the main verb (verhört) and the passive helper (worden). Just like in standard Perfekt sentences, the participles get pushed to the end. The specific action (verhört) always comes right before the grammatical helper (worden).

Why does the noun Verdächtige end with an -e?