What does Acts 23:25 mean?

Lysias, the Roman army tribune, has mastered the useful art of dodging responsibility. While seeing to his duties at the Antonia Fortress on the northern side of the temple mount, he learned of a riot outside the temple. He and his soldiers rescued a man named Paul from a mob bent on killing him. When he enquired as to why Paul deserved such treatment, most of the crowd didn't know (Acts 21:31–36). Lysias then spent the next three days trying to discover what Paul had done besides some vague offense against the Jewish law (Acts 23:29). He did find out two important facts, however: Paul is a Roman citizen and the Jewish leadership is conspiring to murder him (Acts 22:27; 23:19–21). Lysias has no reason to keep Paul in custody, but if he lets him go, a Roman citizen will be killed. He sends Paul to Felix, the governor, in Caesarea Maritima along with an explanatory letter (Acts 23:23–24, 26–30).

"To this effect" means what follows is a paraphrase of the letter, not necessarily the exact wording. The letter includes a summary of the previous three days as well as the notice that Lysias ordered the Jewish leaders to stand before Felix with their accusations. Lysias conveniently leaves out the part where he illegally chained Paul and almost had him whipped (Acts 21:33; 22:24–25).

The high priest Ananias arrives in Caesarea with a few elders and a spokesman who understands the proper format of a Roman court of law. The spokesman offers a vague accusation of rioting and profaning the temple and Paul points out his accuser has offered no actual evidence (Ats 24:1–9, 13).

Felix knows about Christianity and isn't impressed with the accusations. He decides to wait until Lysias arrives with his own evidence, but apparently the tribune has washed his hands of the whole affair and never arrives (Acts 24:22). Felix keeps Paul in custody until he is replaced by Porcius Festus two years later (Acts 24:27).