A trial is underway for a New Hampshire physician assistant accused of writing prescriptions in exchange for kickbacks.The case revolves around the fentanyl spray SUBSYS, a powerful pain medication.Prosecutors said the 43-year-old Christopher Clough’s actions were prompted by greed, while the defense said Clough has always had his patient's best interest in mind.Clough faces eight federal charges for allegedly taking part in a kickback scheme where the physician assistant would receive payments to prescribe SUBSYS.During opening arguments, prosecutors said Clough was payed tens of thousands of dollars by the drug's manufacturer INSYS for writing hundreds of prescriptions between 2013 and 2014.They said the payments were made through speaking fees, the majority of which they claim were sham appearances, sometimes with forged guest lists.Prosecutor Seth Aframe told the jury that the drug company worked on a "no scripts, no program" model, meaning if Clough didn't write the prescriptions, then wouldn't be asked to do the speaking engagements.Defense attorney Patrick Richard said Clough wrote the SUBSYS prescriptions and agreed to speak about the product because he believed in the drug and thought it helped his patients.“He did not agree to get kickbacks and there were no kickbacks,” Richard said.The state's first witness on Wednesday was from the U.S. Food and Drug Administration, who talked about how powerful and potentially dangerous fentanyl pain medication can be if not used properly.Testimony in the case is expected to last for about a week.