The smuggling ring worked this way: Companies with ties to India would typically buy diamonds from India and send them to Hong Kong, and then instruct Hong Kong citizens or Chinese to carry the diamonds illegally, without declaring them at customs, to Shenzhen, where they were marketed to buyers, said a trader identified as Soni Amitkumar Arunkumar in a confession that is part of a judgement by the Intermediate People’s Court of Shenzhen City.