In a closely watched test case, a federal jury in Cleveland on Tuesday found that three of the nation’s largest pharmacy chains, CVS Health, Walmart and Walgreens, substantially contributed to the crisis of opioid overdoses and deaths in two Ohio counties, the first time the retail segment of the drug industry has been held accountable in the decades-long epidemic.

The trial judge will determine how much each company could pay the counties, after as yet unscheduled hearings. New federal data released last week show overdose deaths from illegal opioids such as heroin and street fentanyl have reached record levels during the pandemic.

The verdict — the first from a jury in an opioids case — may be encouraging to plaintiffs in thousands of lawsuits nationwide who are relying on the same legal strategy employed in this case, namely that pharmaceutical companies contributed to a “public nuisance” — a legal term that plaintiffs contend covers the public health crisis created by opioids.

The same argument was rejected twice this month, by judges in California and Oklahoma in cases against opioid manufacturers, who ruled that the companies’ activities were too removed from the overdoses and deaths, and that this application of public nuisance law had been stretched beyond recognition.

But in this case, brought by Lake and Trumbull counties in northeastern Ohio, lawyers used the legal theory successfully, arguing that for years, the pharmacies turned a blind eye to countless red flags about suspicious opioid orders, both at the local counter with patients and at the corporate headquarters, whose oversight requirements were, according to Mark Lanier, the counties’ lead trial lawyer, “Too little, too late.”