One year after health officials sounded the alarm over a deadly carfentanil outbreak in the Twin Cities, a judge on Thursday imposed Minnesota's first federal sentence of a man caught dealing the highly potent synthetic opioid.

Siding with a prosecutor's plea for a prison sentence that acknowledged "the extreme risk of death" behind each of the man's drug deals, Senior U.S. District Court Judge Donovan Frank sentenced John Henry Edmonds to nearly seven years in prison during an hourlong hearing that ended with Edmonds vowing to appeal.

The U.S. Attorney's Office, meanwhile, backed away from a previous charge linking Edmonds to the Feb. 2017 overdose death of Siri Bergstrom, one of 18 people recorded by the Hennepin County Medical Examiner as casualties to carfentanil-related deaths since the start of last year.

Edmonds pleaded guilty earlier this year to five counts of distributing narcotics including heroin, methamphetamine, furanyl fentanyl and carfentanil in a series of undercover purchases carried out by federal drug agents last summer. He admitted that he knew there was fentanyl in the product he sold, but Edmonds has maintained that he did not know he was selling carfentanil at the time.

On Thursday, Assistant U.S. Attorney Surya Saxena told Frank that Edmonds' awareness of trafficking any synthetic opioids at all was reason enough to go beyond calculated federal guidelines that suggested a sentence of roughly four years.

But Edmonds' attorney, Brian Toder, described going beyond that calculation as a "nuclear solution" and, in a previous memo to the judge, characterized Edmonds' case as "hardly a poster case to thwart would-be carfentanil traffickers."

"I simply can't set aside the potency issue," Frank said before handing down his sentence on Thursday in St. Paul.

Recently emerging as a public safety threat in 2016, carfentanil was previously better known as a tranquilizer for large animals like elephants. It is 10,000 times more potent than morphine and between 100 and 200 times more powerful than fentanyl, another synthetic opioid that has increasingly turned up in drug seizures.

"Sadly, highly potent and extremely lethal opioid analogues such as these are becoming more common on the illegal drug market and the devastating societal impact of these substances, even in very small quantities, cannot be overstated," U.S. Attorney Erica MacDonald said in a statement after the sentencing.

Kenneth Solek, assistant special agent in charge at the U.S. Drug Enforcement Administration's Minneapolis office said Thursday that "the trafficking of fentanyl analogues represents a significant threat to public safety" and singled out the investigation, which also involved work by the Minneapolis and Bloomington police departments as "vitally important to our neighborhoods and communities."

Prosecutors say Edmonds was a suspect in the overdose death of 33-year-old Bergstrom. But a drug distribution charge linking Edmonds to her death was dropped after the government concluded that it did not have sufficient evidence to prove he had a role in supplying the carfentanil that killed her.

Saxena cited discrepancies in witness statements, faulty cellphone location data and the possibility of other suspects in agreeing to dismiss the charge. Toder also pointed out that Bergstrom died from an acute carfentanil overdose and that autopsy results revealed no heroin in her body, something he said would have appeared because Edmonds did not sell carfentanil unless it was added to heroin.

Beyond the difficulty in linking overdose deaths to drug dealers, Edmonds' case also underscored the novelty of trying to prosecute — and arrive at the appropriate sentence in — cases involving a drug that few federal courts have considered thus far.

Neither carfentanil nor furanyl fentanyl are listed on "drug equivalency tables" relied on to calculate federal sentencing guidelines.

Toder suggested that carfentanil shouldn't be compared "gram for gram" with other drugs like heroin or methamphetamine, and that potency should only be relevant in cases in which authorities take down stash houses or other large quantities of the drug. In previously filed memos to the court, Saxena, however, warned that treating all fentanyl analogues the same regardless of potency would have understated the societal impact of the drugs.

"Carfentanil is a uniquely dangerous substance," Saxena said. "The substance is so potent there is no guarantee that anyone trying to dose this out will accurately dose this out."

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