What Mlle Gacèlle said above. Narrator must establish himself as subjective. The earlier the better.
Adding. CJ's story can get away with this easier than yours because your genre requires your narrator to stay objective. Imagine a CSI: NY story:
Mary looked guilty.
or
Mary gave a guilty look.
or
Mary fingered her purse guiltily.
Right here, even if Mary is not guilty of the crime at hand, she is assuredly guilty of something because the narrator asserts certainity. This is extremely important because if we find out Mary is not guilty (not even of cheating on her taxes or double-dipping at last night's work party), the writer has cheated us. I dare say, it is required of the writer to reveal at some point "Mary is innocent of the crime at hand, but here's why she was acting guilty" -OR- work really hard on a judgemental-subjective narrator who the reader is convinced may be wrong on several points. In so doing, Mary's innocence causes the reader to go "aha, I knew the narrator was wrong"
Again, my example with Mary is significant in a crime story where tiny clues are meant to help the reader ascertain fact. In another genre, it would probably matter less.