unimpeachable

Difficult or impossible to impeach.

Beyond reproach; blameless.

Beyond doubt; unquestionable.

Not impeachable; not capable of being impeached, accused, censured, or called in question; free from guilt, stain, or fault; blameless; irreproachable.

Not impeachable; not to be called in question; exempt from liability to accusation; free from stain, guilt, or fault; irreproachable; blameless.