The case of a Duluth headshop owner accused of selling banned synthetic drugs went to the jury at 4 p.m. Wednesday in U.S. District Court in Minneapolis.

Jim Carlson, owner of the Last Place on Earth, his girlfriend and his son are charged with 55 counts of illegally selling banned synthetic drugs by allegedly "misbranding" them as herbal incense, bath salts, watch cleaner and other names.

Defense attorney Randall Tigue countered that the chemical compounds the head shop sold were not banned and that Carlson obeyed the law.

A jury of seven women and five men heard closing arguments from both sides on Wednesday during a session that lasted more than four hours. U.S. District Judge David Doty was scheduled to give jury instructions at an afternoon session, after which the jury was expected to being deliberations.

The two-week trial illustrates the nation's battle over what constitutes illegal drugs.

The increasing popularity of synthetic drugs has alarmed authorities, who blame the drugs for thousands of calls to poison-control centers and more than 20 deaths in the United States, including at least two in Minnesota. A Star Tribune investigation in 2011 reported that at least two products sold at the store in 2011 contained chemicals that mimic illegal drugs.

Carlson's girlfriend, Lava Marie Haugen, and his son, Joseph James Gellerman, were employees at the store. The three were charged in December 2012, more than a year after local authorities first identified Carlson's store as a key source of fake pot and other synthetic drugs in Minnesota.

Carlson has sued the federal government to make it reveal the legal basis for its raid on his Duluth store in July 2012, when agents seized a large amount of his inventory, two vehicles and almost $3 million in cash.

Carlson, whose store is currently shuttered pending the outcome of a nuisance lawsuit brought by the city of Duluth, has been an outspoken challenger of the government's right to crack down on synthetic drugs, saying the laws used to prosecute sellers have been "unconstitutionally vague."

Randy Furst • 612-673-4224