In the criminal law of the United States, trials proceed according to the common law system, inherited from the British, which is adversarial and accusatory in nature. An open contest is held between the prosecuting state and the defending individual to determine guilt or innocence according to the law of the land, with the judge acting a neutral arbitrator, sometimes with the help of a jury to determine the facts. This is in contrast to the inquisitorial civil law system, descended from ancient Roman Law, in which the judge takes an active roll in determining the evidence to support a case.
In the United States, the burden of proof is placed on the prosecution, and every defendant is entitled to the presumption of innocence.
Criminal trial begins after charges are brought against the defendant, and the defense and prosecution have agreed on a jury (if the defense wishes a trial by jury). The charges are formally read, and the judge may ask, "Are the counsel ready to proceed?" First the prosecutor, then the defense attorney answer, "Ready, Your Honor," and the trial proceeds.
The prosecution and the defense deliver their opening statements, followed by a brief recess in court. When court resumes, the prosecution begins its "case-in-chief," in which witnesses of the prosecution's choice are brought to the stand for "direct examination" by the prosecution. The testimony of these witnesses will form the substance of the prosecution's case against the defendant. After the direct examination, the defense is permitted a cross-examination, in which the credibility of the prosecution's witnesses is cast in doubt. The prosecution may then redirect the witnesses, attempting to rehabilitate their credibility and restore weight to their testimony. In answer, the defense may re-cross the prosecution's witnesses, again attempting to throw their testimony into doubt. This may continue indefinitely, until both sides are satisfied.
The prosecution ends it's case-in-chief with the words, "Your Honor, the People rest." At this point the defense is permitted to move that criminal charges be dismissed, due to lack of evidence. Dismissal is almost never granted, but the defense will usually request it anyway as a symbolic gesture of the strength of the defendant's case.
Now the defense begins its case-in-chief and calls its own witnesses to the stand to testify for the defendant. This phase mirror's the prosecution's case-in-chief, with direct examination proceeding the prosecution's cross-examination, followed by the defense's redirect, the prosecution's re-cross, and so on, until both sides are satisfied. The defense ends its case-in-chief with the words, "Your Honor, the defense rests."
Now the trial is nearing its conclusion. Before the final motions, however, the prosecution is permitted a "rebuttal," in which surprise witnesses or new evidence found during the course of the trial is presented. Previous witnesses may be recalled at this point, just to reiterate crucial elements of the prosecution's case. After this comes the defense's "rejoinder," in which the defense is likewise called to present any last-minute evidence or witnesses, or recall witnesses to repeat crucial points in favor of the defendant.
The trial is drawing to a close, and now first the prosecution and then the defense are called on to make their summations. Summations are a cross between dramatic speech and legal argument, and are targeted to stick in the hearts and minds of the judge and jury during deliberation. They can be highly emotional, and often vicious.
After summations are delivered by the defense and the prosecution, the judge delivers instructions to the jury on how to proceed, and the jury retires to deliberate. A unanimous verdict is required in most states, with the exception of Louisiana and Oregon, in which a verdict of 10-2 is sufficient. If the jury pronounces the defendant innocent, he is free to go. If guilty, he is immediately remanded into custody.