A.T. Robertson Commentary Acts 26:32

"And Agrippa said unto Festus, This man might have been set at liberty, if he had not appealed unto Caesar." — Acts 26:32 (ASV)

This man might have been set at liberty (Απολελυσθα εδυνατο ο ανθρωπος ουτος). Conclusion of the second class condition (determined as unfulfilled) without αν as in 24:19 because of εδυνατο (verb of possibility, Robertson, Grammar, p. 1014). Note perfect passive infinitive απολελυσθα from απολυω. He certainly "could have been set free." Why was it not done?

If he had not appealed unto Caesar (ε μη επεκεκλητο Καισαρα). Condition of the second class with the past perfect middle indicative (op. cit., p. 1015) of επικαλεω (cf. 25:11f.). But Paul only appealed to Caesar after Festus had tried to shift him back to Jerusalem and had refused to set him free in Caesarea. Festus comes out with no honour in the case. Since Agrippa was a favourite at court perhaps Festus would be willing to write favourably to Caesar.