What highly effective form of information invokes the words of authorities speaking against their own apparent interests?

The correct answer to the following question will be "Reluctant testimony".

Explanation:

Theoretically, reluctant or reticent testimony is preferable to evidence that emanates from such a trustworthy source. Many authors suggest it is equivalent to other impartial evidence, too. It's an extremely effective source of intelligence that conjures up the terms spoken by leaders against certain obvious desires.

Therefore, it's the right answer.