Saying many of those incarcerated in his facilities belong elsewhere, Suffolk County Sheriff Steven Tompkins on Tuesday said the War on Drugs was a "joke" and a "disservice to our nation."

"I think the war on drugs was a flaming, dare I say joke, frankly," Tompkins said at a criminal justice panel discussion hosted by MassINC and The Massachusetts Criminal Justice Reform Coalition. He said, "By putting all of these folks into jail with the idea that they're going to get the big kingpins, it's just done a disservice to our nation."

For decades law enforcement officials have focused on the illicit drug trade, and there are now five times as many people incarcerated as there were in the 1970s, according to a recent report, which found incarcerating people "had relatively little to do" with the major drop in crime since 1991.

Other panelists - former Congressman and prosecutor Bill Delahunt, Northeastern University's Institute on Race and Justice Director Jack McDevitt and Michael Widmer, the former president of the Massachusetts Taxpayers Foundation - broadly agreed that too many people are incarcerated.

Former Attorney General Frank Bellotti and Middlesex District Attorney Marian Ryan were unable to make the event, said MassINC President Greg Torres, who said he hoped Suffolk District Attorney Dan Conley would be able to make an appearance - though Conley also was unable to make it. Conley has defended laws that demand a minimum sentence for those convicted of a certain crime, saying judges who deliver sentences are disconnected from communities burdened by high crime.

Brennan Center for Justice Senior Counsel Lauren-Brooke Eisen told the crowd in the Gardner Auditorium that the center investigated several theories for the drop in crime from the early 1990s and found the maturing age of the nation's population, new tacks on policing and less alcohol consumption all played a role.

"In a nutshell, we do not know with precision what caused the crime decline, but we do know that the growth in incarceration played a very limited effect," Eisen said, crediting the incarceration of 1.1 million more people over the course of roughly two decades for about 5 percent of the reduction in the 1990s and zero percent in the 2000s.

Massachusetts was one of the states that through the 2000s saw a reduction in both incarceration and crime, according to the study. Since 1991, violent crime across the country has fallen by 51 percent and property crime has fallen 43 percent.

The study found the country's "archipelago" of prisons and jails costs $80 billion annually to operate and people of color are disproportionately incarcerated.

Tompkins, whose facilities handle suspects and offenders from in and around Boston, said many people incarcerated should be in a mental health or substance abuse bed.

Tompkins said individuals in his facility have an average fifth or sixth grade math and reading level. Tompkins, who is black, said 65 percent of the population "looks like me," while 85 percent have some involvement in drugs and 42 percent have some form of mental illness.

Governmental belt-tightening will force lawmakers to consider alternatives to ballooning incarceration that occurred during the "roaring economy" of the 1990s, Widmer said.

"There's a new fiscal reality in which we're going to have to make tough choices," Widmer said. Widmer said the bipartisan movement calling for reduction in mandatory minimum sentences is "what happens when there's a failed policy - mass incarceration - that goes on for so long."