The six defendants (defendants) in this case were charged with dealing in marijuana. One of the issues was whether the marijuana had been imported from outside the United States, namely Colombia. The prosecution called John de Pianelli to testify as an expert witness that the marijuana dealt by defendants came from Colombia. De Pianelli allegedly helped the defendants’ smuggling ring by unloading it and smoking some of the marijuana each time to make sure it was Colombian. De Pianelli said he had smoked marijuana over 1,000 times and that he had been asked to identify marijuana over 100 times and had never made a mistake. He based his identification on the marijuana’s appearance, smell and the effect of smoking it. The defendants objected to de Pianelli as an expert witness. The district court permitted de Pianelli’s testimony and the defendants were convicted. The defendants appealed.