=The Trial Jury.=—The other jury is known as the trial jury or petit jury and practically always consists of twelve persons. The method of selecting a trial jury is, in general, as follows: Some public official who is entrusted by the law with this duty makes a list of the persons who are liable for jury service. This list is usually compiled from the roll of voters, leaving off all persons (such as lawyers, physicians, public officials, and so on) who are exempted by law from jury duty. From this list a certain number of names, perhaps fifty to a hundred, are then selected, usually by lot. These individuals are thereupon summoned to court, where they form what is known as the jury panel. One by one their names are called in court and the lawyers on either side of the case are given an opportunity to state their objections.[149] When twelve persons have been found to whom there is no objection from either side, these twelve constitute the jury and proceed to hear the facts of the case. [Sidenote: Its work.] The trial jury, however, may hear only such evidence as the judge permits it to hear, for the question whether any item of evidence can be permitted is a question of law. The value of the evidence, after the judge has allowed the jury to hear it, is for the jury to determine. [Sidenote: Jury procedure.] The usual procedure in a jury trial, therefore, is this: When the jury has been chosen and sworn to decide the issue fairly, the prosecuting attorney (or, in a civil case, the counsel for the plaintiff) states briefly to the court what he intends to prove. Then the witnesses for the prosecution, or for the plaintiff, are called, put upon oath, and questioned. As each witness finishes his direct testimony the defendant’s counsel takes him in hand for cross-examination. The purpose of this cross-examination is to test the witness, to see if he is telling the truth, or to induce him to say things which will weaken his original testimony.[150] When the witnesses for the prosecution have finished, the witnesses for the defendant are called and they likewise are cross-examined by the other side. After all the testimony is concluded the counsel on both sides make addresses to the jury, the judge explains to the jurymen the points of law bearing on the case, and the jury retires to consider its verdict. This it does in secret, remaining in a room which no one is allowed to enter or leave. [Sidenote: Second jeopardy.]