Police began an investigation into a heroin trafficking operation allegedly being conducted in a Northwest Washington hotel. An informant made heroin purchases from suspects. Search warrants for the two hotel rooms were obtained and executed. They found Sherman W. Beverly D was seated in the room. In front of Beverly's chair, about one inch from the edge of the bed was a white-framed mirror on which there was a quantity of white powder (later found to be 1,854.5 milligrams of a mixture containing 4-7% heroin). To the right of the mirror, in front of D's chair, was a flat square cardboard record album cover, on which there was also a quantity of white powder (later determined to be 1,824 milligrams of a mixture containing 4-7% heroin). Between them lay 93 new gelatin capsules and 81 used gelatin capsules. To the left of the mirror lay 67 capsules filled with a white powder (later found to be a total of 3,650 milligrams containing 4-7% heroin). Toward the far edge of the bed, there was a woman's stocking stretched over a wire coat hanger (called a cutting screen). Next to the cutting screen was an unopened package containing about 10 hypodermic syringes and needles. Lying on the album, in front of D's chair, was an ace of hearts cut in half (often called a cutting card). Near the pillow were a set of keys that were found to fit the door of room 15. Under the pillow was a 38-caliber Smith & Wesson pistol. At his trial, there was evidence that D was also a dealer. D contended that he was a mere addict and should not be held responsible for being in possession of the drug. The prosecution conceded that D was an addict. The evidence was in conflict of whether D was a dealer as well. The trial court refused D's expert testimony on the nature of D's addiction and declined to instruct the jury that a nontrafficking addict could not be convicted under the statute charged. D was convicted and appealed. D contends that his conviction was improper because he is a heroin addict with an overpowering need to use heroin and should not, therefore, be held responsible for being in possession of the drug.