Hello! The 8th juror is a thoughtful man who aims to see justice done; he is the only dissenting voice during the first vote. He argues that he would like to deliberate further before he makes his decision. The 8th juror believes that all the jurors owe the boy an opportunity to have his voice heard before they send him to the electric chair, as the boy is only nineteen years old and has had a hard start in life.
The jurors are incredulous that he would have any doubts as to the boy's guilt, and the 8th juror tells everyone that they should vote again. He promises that if there are still eleven guilty votes, he would support a guilty verdict. However, during this second vote, the 9th juror changes his verdict, which frustrates most of the other jurors. Why does the 9th juror change his mind? Whether due to the influence of the 8th juror or to his dawning uneasiness about the jurors' rush to judgment, the 9th juror is starting to recognize the grave responsibility everyone has been entrusted with. He now wants to ascertain guilt beyond a reasonable doubt before the young man is sent to the electric chair.
The 9th juror's dissenting vote appears to have a domino effect on the rest of the jury. You can say that he becomes an advocate for the boy; he also begins to doubt the old man's testimony (about hearing the boy yell out that he was going to kill his father above the noise of the passing train). With both jurors now advocating for the boy, the tide changes. The lone holdouts are eventually reduced to the 3rd, 4th, and 10th juror. The 3rd juror is the last one to change his vote.
So, is the 8th juror the only one who values the life of the boy? The short answer is no. The 9th juror comes closest to sharing the 8th juror's principles; the rest of the jurors are in turn convinced through careful deliberation. I would say that the 3rd juror has the hardest time being objective; at the end of the play, he finally changes his vote, but only due to pressure. One gets the impression that he is not entirely convinced that the boy is guiltless.
Thanks for the question!