One of the biggest players accused of kick starting America's opioid addiction was in a Boston Court Monday.

Federal prosecutors spent their first day telling jurors that John Kapoor of Chandler, Arizona and Insys Therapeutics Inc. founder was motivated by greed and sold the addictive fentanyl opioid spray like he was running a "criminal enterprise."

Kapoor's attorneys down played the product's role in the nation's opioid epidemic, insisting his client was motivated to introduce the pain killer to the public in 2013 after watching his wife suffer from metastatic breast cancer eight years earlier.

The 75-year-old founder and four other former employees are accused of paying doctors millions of dollars in kickbacks to over-promote the highly addictive drug to other doctors and patients, which prosecutors argue is at the core of the nation's opioid crisis.

Kapoor could face up to 20 years in prison on racketeering charges.

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