What point does Juror #8 make by questioning Juror #4 about what movie he saw?

The 8th Juror attempts to break apart the testimony of the arresting police officer that the defendant was unable to name the movies that he had claimed to have seen that evening. He asserts that possibly the defendant just forgot the names of the films and who was in them “under great emotional distress.” He illustrates this point by asking 4th Juror what he saw several nights ago at the movies. 4th Juror is unable to respond accurately, and the point is made.