21 U.S.C. Sec. 844 Simple Possession — Elements is a federal law that outlines the legal elements that must be met to prosecute someone for simple possession of a controlled substance. The law states that in order to prove simple possession, the prosecution must prove that the accused knowingly or intentionally possessed a controlled substance, without a valid prescription. The types of simple possession elements include knowing possession, intentional possession, and possession of a controlled substance without a valid prescription.