Although a few individuals and corporations bring private prosecutions, the vast majority of prosecuting in England and Wales is done by the Crown (representing the State), and most of those via the Crown Prosecution Service (CPS) whose independent reviewing lawyers will take the material given to them by the police or some investigating authority and asses it to determine whether or not there is a realistic prospect of obtaining a conviction in court. Find out more about the Crown Prosecution Service here.
In England and Wales, it is the Prosecution who brings the case against a defendant. It is therefore for the prosecution to prove the case (they bear the so-called ‘burden of proof’), and they must do so to a standard whereby the court, whether Judge(s) or jurors, must be satisfied so that they are sure of the defendant’s guilt. It is important to remember that no defendant is ever required to prove their innocence.
Because the Prosecution bring the case, they also take charge of the general shape and structure of the case; they will decide how it is charged and will introduce it in court.
As a prosecution barrister you will be in charge of conducting the trial and calling the evidence in the case. The barrister will argue all legal points that arise, cross examine the defendant to show he or she is not telling the truth, and to argue the prosecution case to the jury or judge as to why the defendant is guilty.