Possession : The actual, physical Possessio n, or the constructive Possession (which shall be found only if the  Person  has exclusive  control  or intends  to exercise  control  over the Prohibited  Substance  or Prohibited Method or the premises in which a Prohibited Substance or Prohibited Method exists);  provided, however, that if the Person does not have exclusive control over the Prohibited Substance or Prohibited Method or the premises in which a Prohibited Substance or Prohibited Method exists, constructive Possession shall only  be found  if the Person  knew  about  the presence  of the Prohibited  Substance  or Prohibited  Method  and intended to exercise control over it.