What testimony has been given in court by the old man who lives in the same building as the suspect in Twelve Angry Men by Reginald Rose?

After the jurors cloister themselves in the jury room and they take a vote, Juror No. 8 is the only one who votes "Not Guilty." When Juror No. 12 suggests that they convince him, No. 3, a very opinionated and intolerant man, goes over the facts. First, he refers to the neighbor's testimony.

The old man, who lives on the second floor under the room where the murder occurred, has testified that he heard noises...

After the jurors cloister themselves in the jury room and they take a vote, Juror No. 8 is the only one who votes "Not Guilty." When Juror No. 12 suggests that they convince him, No. 3, a very opinionated and intolerant man, goes over the facts. First, he refers to the neighbor's testimony.

The old man, who lives on the second floor under the room where the murder occurred, has testified that he heard noises that were quite loud coming from the upstairs apartment. To him, there seemed to be an argument going on; then, he heard the boy say to his father, "I'm gonna kill you." Right after this, he heard someone falling; so, he ran to his door to look out, and he saw the suspect running down the stairs and out of the house. After witnessing the boy's running away, the old man phoned the police. When the police arrived, the father was found with a knife in his chest.

This testimony seems rather damning, but it is the perseverance of Juror No. 8 in examining and re-examining the testimony and other facts of the case which lead them to feel that there is reasonable doubt about the son's being the one who stabbed his father.