Section 160.15. Robbery in the first degree

A  person  is  guilty  of robbery in the first degree when he forcibly
  steals property and when, in the course of the commission of  the  crime
  or  of  immediate  flight  therefrom,  he  or another participant in the
  crime:
    1. Causes  serious  physical  injury  to  any  person  who  is  not  a
  participant in the crime; or
    2. Is armed with a deadly weapon; or
    3. Uses or threatens the immediate use of a dangerous instrument; or
    4.  Displays  what  appears  to be a pistol, revolver, rifle, shotgun,
  machine gun or other firearm; except that in any prosecution under  this
  subdivision,  it  is  an affirmative defense that such pistol, revolver,
  rifle, shotgun, machine gun or other firearm was  not  a  loaded  weapon
  from  which  a shot, readily capable of producing death or other serious
  physical  injury,  could  be  discharged.  Nothing  contained  in   this
  subdivision shall constitute a defense to a prosecution for, or preclude
  a  conviction  of,  robbery  in  the second degree, robbery in the third
  degree or any other crime.
    Robbery in the first degree is a class B felony.