What is the policy of admitting propensity evidence in a criminal case?

The policy reasons for the admission of propensity evidence under section 1109 were also addressed in People v. Poplar (1999) 70 Cal.App.4th 1129, 83 Cal.Rptr.2d 320 ( Poplar ), where defendant was convicted of the forcible rape of his girlfriend. He argued that his prior acts of domestic violence were improperly admitted at trial because the rape prosecution was not an offense involving domestic violence, and section 1109 and Penal Code section 13700 " 'refer to the classic kind of pushing, shoving, hitting, slapping, punching' and not to 'a specific sexual offense such as rape.' " ( Poplar at p. 1138, 83 Cal.Rptr.2d 320.)