Section 17-325.1. Failure to display and produce license or permit; presumptive evidence of unlicensed or unpermitted activity

a.  In  any  civil  or criminal action or proceeding, failure by a food vendor who is
  required to be licensed pursuant to the provisions of  this  chapter  to
  display  and  exhibit  upon demand a food vendor's license in accordance
  with the provisions of this chapter to any police officer, public health
  sanitarian or other authorized officer or employee of the department  or
  other city agency shall be presumptive evidence that such food vendor is
  not duly licensed.
    b.  In  any civil or criminal action or proceeding, the failure of any
  vehicle or pushcart which is required to be permitted  pursuant  to  the
  provisions  of  this  chapter  to have a permit plate affixed thereto in
  accordance with the provisions of  this  chapter  shall  be  presumptive
  evidence that such vehicle or pushcart is not duly permitted.