James Carlson could pay a huge price for the very public defiance that gained him state and national notoriety as a seller of synthetic drugs from his head shop in Duluth.

Calling him “arguably the most vocal proponent of synthetic drugs in the United States,” federal prosecutors in Minneapolis are seeking a 20-year sentence for Carlson, who was convicted last October. Sentencing is scheduled for Thursday, though Carlson’s attorney is seeking a delay until at least next week.

Assistant U.S. Attorney Surya Saxena told U.S. District Judge David Doty in court documents that a stiff sentence will send an important message to those who mistakenly believe that selling synthetic drugs is legal.

“A strong criminal punishment for the synthetic industry’s most vocal advocate would give pause to these would-be synthetic drug traffickers, and is likely to reduce future synthetic drug trafficking,” Saxena wrote.

Carlson, 57, was convicted by a federal jury on 51 of 55 felony counts for his role in the sale of synthetic drugs at the Last Place on Earth, the shop that once drew long lines of addicts and recreational users. His girlfriend Laura Haugen, 34, was convicted of four counts.

The store became a headache to downtown businesses and public officials, who followed the case with interest.

“It really has been a story that has occupied the attention of our city for many years,” Duluth Mayor Don Ness said Wednesday. Carlson needs “to be held to account for the devastation he created,” Ness said, especially for “the lives that were negatively impacted, and in some cases destroyed by the sale of these drugs.”

In making the case for a long sentence, federal prosecutors attached and liberally quoted from a sworn statement by Dr. Nicholas Van Deelen, medical director at the emergency department of St. Luke’s Hospital in Duluth.

Van Deelen said his emergency department used to treat two to three people a week, most of whom bought synthetic drugs at Carlson’s store and arrived with symptoms that required “the use of rare measures such as physical restraint, admission to the intensive-care unit, or admission to a mental health ward.”

In the year since the Last Place on Earth was closed by police on July 19, 2013, St. Luke’s has seen a total of 41 synthetic drug patients, compared with 75 per month when the store was open, about a 95 percent decrease, he wrote.

Defense seeks three years

Randall Tigue, Carlson’s attorney, asks for a three-year sentence, arguing that Carlson is a nonviolent offender with no criminal record, and has medical problems as result of gastric bypass surgery, which have worsened during his time in jail awaiting sentencing.

Tigue cited the 2013 case of a Florida man who manufactured and marketed synthetic drugs nationwide — “conduct far more egregious” — and got only a three-year sentence.

Much of the pre-sentence debate has focused on the strength of the drugs that Carlson sold.

Saxena cited a probation report that concluded that Carlson’s sentence should be based on the massive amount of the synthetic drugs he distributed, the equivalent of 490,056 pounds of marijuana.

Tigue responded, “There is … absolutely no evidence to support the proposition that any of the controlled substances are similar in chemical structure to THC,” the active ingredient in marijuana.

Indeed, Saxena argues that the synthetic drugs are far “more potent, dangerous and have a higher potential for abuse” than marijuana.

While the prosecutors say Haugen had a major role in the business and had “general management responsibilities,” her attorneys, John Markham II and Richard Holmstrom, contend her role was limited and she believed Carlson when he told her the drugs were legal. They said she also suffers from medical and mental health problems and has been diagnosed as having multiple sclerosis. They say she should receive little or no prison time.

Carlson’s best hope may be the inevitable appeal to the Eighth Circuit of Appeals, where Tigue can be expected to renew arguments made during the trial, that there is much dispute over what constitutes an illegal synthetic drug, because their compositions are constantly being reformulated, putting them beyond the reach of vaguely written federal regulatory laws. The 8th Circuit, however, does not have a reputation of overturning criminal convictions.