YOU SAID:

my great aunt had to have been going home early last night if she wasn't going to be judged

INTO JAPANESE

大叔母が裁かれなければ、昨夜は早く家に帰っていたに違いない

BACK INTO ENGLISH

If my aunt hadn't been judged, I must have gone home early last night

INTO JAPANESE

もし叔母が裁かれていなかったら、私は昨夜早く家に帰っていたに違いない

BACK INTO ENGLISH

If my aunt hadn't been judged, I must have gone home early last night