CHARLESTON, WV (WOWK) — Witness testimony began Tuesday in the nation’s first federal lawsuit against three big opioid distributors, for their alleged role in the opioid crisis.

Dr. Corey Waller testified on behalf of the city of Huntington and Cabell County.

The city and county’s lawsuit alleges these three opioid distributors – AmerisourceBergen, Cardinal Health and McKesson dumped millions of pills into the community, causing thousands of deaths and overdoses.

Waller, a Michigan doctor who is an addiction expert, took the witness stand at Robert C. Byrd Federal Court in Charleston.

He explained addiction to the court, specifically how after a while the brain cannot tell the difference between prescription opioid pills and heroin and wants more of it.

Waller cited a medical article “Epidemiology of the U.S. opioid crisis: The importance of the vector,” by Wilson Compton, which says clinicians and pharmaceutical companies involved in the marketing and distributing of opioid pills were factors for the opioid epidemic.

Under cross-examination by the defense, Waller was then questioned about a shift in pain management practices starting in the early eighties.

The attorney specifically pointed to an article in the New England Journal of Medicine called “The Quality of Mercy” and a passage that reads “Pain is soul-destroying, no patient should have to endure pain unnecessarily. the quality of mercy is essential to the practice of medicine, here of all places, it should not be strained.”

Defense exhibits also showed memos and newsletters from the West Virginia Board of Medicine that stated physicians would not be subject to disciplinary action for prescribing opioids if documentation was taken.

But Dr. Waller argued this memo was overattributed and it did not mean doctors could write whatever they wanted.

More witnesses will take the stand this week including Dr. Rahul Gupta, West Virginia’s former public health officer, and Huntington fire chief Jan Rader who was on the front lines of the opioid crisis

The trial is expected to last 12 weeks.