Technically NO because the so-called vicitm of the crime is not the one prosecuting the case. In Chicago, the Cook County State's Attorney's Office is responsible for prosecuting violations of Illinois law, such as the armed robbery in your example. However, it is routine for the prosecutor to consult the so-called "victim"before they decide how they would ultimately like to deal with the case; that is whether they want to offer a reduction in charge if the defendant pleads guilty, or certainly if intend to dismiss it. In your example, in an arm
ed robbery case (especially with a firearm) its very rare to just dismiss the case, however without the cooperation of a witness, it may be very difficult for the proseuctor to prove its case. On the other hand, in a typical domestic dispute where someone is charged with domestic battery or assualt, it is common for the so-called victim to come to court, tell the prosecutor that they do not want to press charges or proceed with the case, and it will likely be dismissed.