(NewsNation Now) — Attorneys for four major pharmacy chains are back in federal court Tuesday in the first trial in their potential role in the nation’s opioid epidemic.

Retail pharmacy chains contributed to a deadly and expensive public nuisance, an attorney for two Ohio counties said in an opening statement Monday in federal court in Cleveland.

“They’re going to say, ‘We’re not any part of the problem,’” attorney Mark Lanier said. “They’re going to blame everyone but themselves.”

Attorneys for CVS, Walgreens, Walmart and Giant Eagle are expected to give opening statements Tuesday morning with the counties putting on their first witness, a CVS employee, later in the day.

Attorneys for the four pharmacy chains have argued the companies didn’t manufacture the drugs and that their pharmacies were filling prescriptions written by physicians for patients with a legitimate medical need.

“Pharmacists fill the prescriptions, they don’t tell doctors what to prescribe,” Casper Stoffelmayr, an attorney for Walgreens said in an opening statement.

Lake and Trumbull counties say the cost of abating the ongoing crisis is $1 billion for both counties.

This is the first time pharmacy companies have gone to trial to defend themselves. The trial, which is expected to last around six weeks, could set the tone for similar claims against retail pharmacy chains by government entities across the U.S.