Proponents of loosening marijuana laws argue it’s less harmful than other drugs, including alcohol and nicotine. Opponents counter that marijuana’s health effects aren’t adequately understood, and that it can serve as a “gateway” to harder drugs.

Rep. Lane Roberts, R-Joplin, a former police chief and director of the Missouri Department of Public Safety, said the change could result in an increase in the use of the drug.

“Are we diminishing the deterrent by diminishing the penalty?” Roberts said.

Dan Viets, a Columbia lawyer whose practice includes defending marijuana cases, said attitudes about the drug have evolved since tough-on-crime laws were put on the books.

“It is clear that a solid majority of Americans across the country favor legalization,” Viets said.

According to a nonpartisan analysis of the legislation, 30 people were incarcerated in 2018 for marijuana violations, with an average sentence of seven years. An additional 383 were given probation, with an average term of three years.

The full impact of the proposed change would occur by 2026, with an estimated 90 fewer people incarcerated and more than 1,200 fewer people on probation.