Scientific jury selection, often abbreviate SJS, is the use of social science techniques and expertise to choose favorable juries during a criminal or civil trial. Scientific jury selection is used during the jury selection phase of the trial — when lawyers have the opportunity to question jurors and they and the judge choose which people will be on the jury. It almost always entails an expert's assistance in the attorney's use of peremptory challenges — the right to reject a certain number of potential jurors without stating a reason — during jury selection. The practice is currently confined to the American legal system.