Dr. Nelson Onaro conceded last summer that he’d written illegal prescriptions, although he said he was thinking only of his patients. From a tiny, brick clinic in Oklahoma, he doled out hundreds of opioid pills and dozens of fentanyl patches with no legitimate medical purpose.

“Those medications were prescribed to help my patients, from my own point of view,” Onaro said in court, as he reluctantly pleaded guilty to six counts of drug dealing. Because he confessed, the doctor was likely to get a reduced sentence of three years or less in prison.

But Onaro changed his mind in July. In the days before his sentencing, he asked a federal judge to throw out his plea deal, sending his case toward a trial. For a chance at exoneration, he’d face four times the charges and the possibility of a harsher sentence.

Why take the risk? A Supreme Court ruling has raised the bar to convict in a case like Onaro’s. In a June decision, the court said prosecutors must not only prove a prescription was not medically justified ― possibly because it was too large or dangerous, or simply unnecessary ― but also that the prescriber knew as much.

Suddenly, Onaro’s state of mind carries more weight in court. Prosecutors have not opposed the doctor withdrawing his plea to most of his charges, conceding in a court filing that he faces “a different legal calculus” after the Supreme Court decision.

The court’s unanimous ruling complicates the Department of Justice’s ongoing efforts to hold irresponsible prescribers criminally liable for fueling the opioid crisis. Previously, lower courts had not considered a prescriber’s intention. Until now, doctors on trial largely could not defend themselves by arguing they were acting in good faith when they wrote bad prescriptions. Now they can, attorneys say, although it is not necessarily a get-out-of-jail-free card.

“Essentially, the doctors were handcuffed,” said Zach Enlow, Onaro’s attorney. “Now they can take off their handcuffs. But it doesn’t mean they are going to win the fight.”

The Supreme Court’s decision in Ruan v. United States, issued June 27, was overshadowed by the nation-shaking controversy ignited three days earlier, when the court erased federal abortion rights. But the lesser-known ruling is now quietly percolating through federal courthouses, where it has emboldened defendants in overprescribing cases and may have a chilling effect on future prosecutions of doctors under the Controlled Substances Act.

In the three months since it was issued, the Ruan decision has been invoked in at least 15 ongoing prosecutions across 10 states, according to a KHN review of federal court records. Doctors cited the decision in post-conviction appeals, motions for acquittals, new trials, plea reversals, and a failed attempt to exclude the testimony of a prescribing expert, arguing their opinion was now irrelevant. Other defendants have successfully petitioned to delay their cases so the Ruan decision could be folded into their arguments at upcoming trials or sentencing hearings.

David Rivera, a former Obama-era U.S. attorney who once led overprescribing prosecutions in Middle Tennessee, said he believes doctors have a “great chance” of overturning convictions if they were prohibited from arguing a good faith defense or a jury was instructed to ignore one.

Rivera said defendants who ran true pill mills would still be convicted, even if a second trial was ultimately required. But the Supreme Court has extended a “lifeline” to a narrow group of defendants who “dispensed with their heart, not their mind,” he said.

“What the Supreme Court is trying to do is divide between a bad doctor and a person who might have a license to practice medicine but is not acting as a doctor at all and is a drug dealer,” Rivera said. “A doctor who is acting under a sincerely held belief that he is doing the right thing, even if he may be horrible at his job and should not be trusted with human lives ― that’s still not criminal.”

The Ruan decision resulted from the appeals of two doctors, Xiulu Ruan and Shakeel Kahn, who were separately convicted of running pill mills in Alabama and Wyoming, respectively, then sentenced to 21 and 25 years in prison. In both cases, prosecutors relied on a common tactic to show the prescriptions were a crime: Expert witnesses reviewed the defendants’ prescriptions and testified that they were far out of line with what a reasonable doctor would do.

But in writing the opinion of the Supreme Court, then-Justice Stephen Breyer insisted the burden of proof should not be so simple to overcome, remanding both convictions back to the lower courts for reconsideration.

Because doctors are allowed and expected to distribute drugs, Breyer wrote, prosecutors must not only prove they wrote prescriptions with no medical purpose but also that they did so “knowingly or intentionally.” Otherwise, the courts risk punishing “conduct that lies close to, but on the permissible side of, the criminal line,” Breyer wrote.

To defense attorneys, the unanimous ruling sent an unambiguous message.

“This is a hyperpolarized time in America, and particularly on the court,” Enlow said. “And yet this was a 9-0 ruling saying that the mens rea ― or the mental state of the doctor ― it matters.”

Maybe nowhere was the Ruan decision more pressing than in the case of Dr. David Jankowski, a Michigan physician who was on trial when the burden of proof shifted beneath his feet.

Jankowski was convicted of federal drug and fraud crimes and faces 20 years in prison. In an announcement of the verdict, the DOJ said the doctor and his clinic supplied people with “no need for the drugs,” which were “sold on the streets to feed the addictions of opioid addicts.”

Defense attorney Anjali Prasad said the Ruan ruling dropped before jury deliberations in the case but after prosecutors spent weeks presenting the argument that Jankowski’s behavior was not that of a reasonable prescriber — a legal standard that on its own is no longer enough to convict.

Prasad cited the Ruan decision in a motion for a new trial, which was denied, and said she intends to use the decision as a basis for a forthcoming appeal. The attorney also said she is in discussion with two other clients about appealing their convictions with Ruan.

“My hope is that criminal defense attorneys like myself are more emboldened to take their cases to trial and that their clients are 100% ready to fight the feds, which is no easy task,” Prasad said. “We just duke it out in the courtroom. We can prevail that way.”

Some defendants are trying. So far, a few have scored small wins. And at least one suffered a crushing defeat.

In Tennessee, nurse practitioner Jeffrey Young, accused o trading opioids for sex and notoriety for a reality show pilot, successfully delayed his trial from May to November to account for the Ruan decision, arguing it would “drastically alter the landscape of the Government’s war on prescribers.”

Also in Tennessee, Samson Orusa, a doctor and pastor who last year was convicted of handing out opioid prescriptions without examining patients, filed a motion for a new trial based on the Ruan decision, then persuaded a reluctant judge to delay his sentencing for six months to consider it.

And in Ohio, Dr. Martin Escobar cited the Ruan ruling in an eleventh-hour effort to avoid prison.

Escobar in January pleaded guilty to 54 counts of distributing a controlled substance, including prescriptions that caused the deaths of two patients. After the Ruan decision, Escobar tried to withdraw his plea, saying he’d have gone to trial if he’d known prosecutors had to prove his intent.

One week later, on the day Escobar was set to be sentenced, a federal judge denied the motion.

His guilty plea remained.

Escobar got 25 years.

KHN (Kaiser Health News) is a national newsroom that produces in-depth journalism about health issues. Together with Policy Analysis and Polling, KHN is one of the three major operating programs at KFF (Kaiser Family Foundation). KFF is an endowed nonprofit organization providing information on health issues to the nation.