After verbs of saying, thinking, knowing and perceiving, Latin reports a statement as an accusative subject with an infinitive verb; translate it as a "that" clause.
Look for a verb of saying, thinking, knowing or perceiving (dico, puto, scio, comperio, memini, intellego), or an impersonal such as constat, with a noun or pronoun in the accusative and an infinitive. The accusative is the subject of the infinitive.
Translate with "that" and make the infinitive an ordinary verb, with the accusative as its English subject: nec laedi posse me … compertum habeo "I have found that I cannot be harmed".