Tā yìduàn duìfāng yǒu zuì, què ná bù chū rènhé zhèngjù.
He assumed the other party was guilty but couldn't produce any evidence.
Tips
usage
臆断 is formal and negative in tone. It implies reaching a conclusion based on subjective feeling rather than fact or logic. It is stronger than 猜测 (to guess) and closer to 'prejudge' or 'assume without basis'.
memory
臆 refers to the chest/heart (the seat of subjective feeling in classical thought), and 断 means 'to judge/decide'. To 臆断 is to 'judge from the heart' - i.e., from gut feeling rather than evidence.
