For what reason did Juror #8 not vote guilty during the initial jury vote?

8th Juror presents several hypothetical situations, based on the father’s criminal background, that could have gotten him killed that evening. Next, he attempts to discount the testimony by the old man living downstairs by deducing that, because of the sound made by the elevated train passing by, there’s no way he could have heard with certainty screaming and a body hitting the floor. 9th Juror identifies with the poor old man, believing that he might just be trying to feel important. 8th Juror concludes by saying that even if he did hear him say, “I’m gonna kill you,” that very well could be taken out of context as just a figure of speech.