In Michigan, the message about the state's mandatory sentencing law was plain and simple: "One With a Gun Gets You Two." Florida warned gun violators: "Think twice. Three years to life." And on Pennsylvania television channels, the cool and mean voice of movie bad guy Jack Palance intones: "From now on, a crime with a gun means you're in for five years . . . No deals. No parole. No exceptions."

And five years, says Palance, "is a ton of time."

On Sept. 14, the citizens of the District of Columbia will decide whether to approve a proposed mandatory minimum sentencing law just as tough as the one Palance describes, not only for most persons convicted of using a firearm in a violent crime but also for many found guilty of trafficking in dangerous drugs.

Supporters of the measure, called Initiative 9 because it is the ninth proposed here since voters approved the procedure in 1977, contend that fixed sentences will get serious offenders off the streets and will deter others because they will know, for certain, that they will spend time in jail.

"We have to say there are certain crimes that we will not tolerate," said D.C. City Council member and mayoral candidate John Ray (D-At Large), who organized the effort to collect more than 24,000 citizens' signatures to get the measure on the primary ballot.

"One thing I do know is that punishment deters crime and if punishment doesn't deter crime, then we might as well let everyone out," Ray said.

Opponents argue, however, the proposed law would prohibit judges from considering circumstances surrounding a crime that might justify a lesser sentence.

They say the local court will be strangled in demands for jury trials from defendants unwilling to plead guilty to charges that carry mandatory prison terms, and that the already overcrowded jails will become even more crowded.

"I'm not so sure the community has a real sense of how tough this city is on armed offenders," said former U.S. Attorney Charles F.C. Ruff, who is actively opposing Initiative 9.

Ruff and a broad coalition of opponents also cite Justice Department statistics that show that the District already imprisons more convicted persons than any other jurisdiction in the country -- four times the average -- and that each new prisoner costs $15,000.

Supporters of the initiative argue that those figures are misleading because District figures, unlike those for the states, included the city jail population and therefore were inflated unfairly.

Ruff, the city's top criminal prosecutor for more than three years, contends that mandatory sentencing does not have a "discernible effect" on the rate of violent crime or armed offenses. He says that the proposed D.C. law is poorly drafted and conflicts with existing sentencing procedures here, including those for repeat offenders.

The initiative provides for a mandatory minimum prison sentence of five years for a person convicted for the first time of using a gun during the commission of a crime of violence, and 10 years for a repeat offense. The law would not apply to persons sentenced under the federal Youth Corrections Act, which allows indeterminate sentences for defendants under the age of 22.

The initiative provides a four-year minimum sentence for persons convicted of selling or distributing illegal narcotic drugs, such as heroin; a 20-month minimum for sales or distribution of illegal non-narcotic drugs, such as PCP or cocaine, and a one-year minimum for sales of controlled substances, including marijuana, if the value of the amount sold exceeds $15,000.

Judges may waive the mandatory sentences for first offenders who were drug addicts and who sold or distributed drugs to help support that habit.

In order for the initiative to become law, it first must be approved by a majority of voters in the Sept. 14 primaries and then survive a review by Congress.

Mandatory minimum sentencing laws -- 32 states have adopted them in various forms for gun violations -- have become a favorite topic of professional researchers whose job is to think about notions of crime and punishment. But their work has produced sharply divided views. Opposing camps each can point to studies they say back their position on Initiative 9.

Recently, the opponents have focused on a policy brief prepared by a study arm of the Justice Department, which examined mandatory sentencing laws in New York (for drug offenses) and in Massachusetts (for carrying a gun).

A Justice Department press release said the study concluded that states should "proceed with caution" in passing such measures because "hoped-for gains may be offset by increased burdens on other areas of the criminal justice system."

The study, prepared for the National Institute of Justice by a Boston-based consulting firm, concludes that "ambiguous statistical results" about the effects of the laws in New York and Massachusetts should be a warning to those who promise that such laws "will deliver certain punishment, harsher penalties and reductions in crime."

" . . . Such promises can only be based on faith and not fact," the study concludes.

"I read the study you're talking about and it is clear to me the person who wrote that study is not in favor of mandatory sentencing laws," said Ray.

"The New York law didn't fail because it didn't work, it was just never enforced," he added, contending that prosecutors were reluctant to enforce the law because it aimed too harsh a penalty at drug possessors. The proposed new statute for the District "is clear we are only after persons selling drugs . . . for profit," he said.

Ray says that another study -- also funded by the National Institute of Justice and conducted by researchers from Boston University Law School -- shows that the Massachusetts law had a "tremendous impact" on reducing armed assaults, homicides and armed robberies.

A brief introduction to that study, however, notes that the results were "mixed" and points out that while gun assaults decreased, non-gun assaults substantially increased.

In Wayne County, Mich., which encompasses the city of Detroit, there was a dramatic drop in gun crimes after the mandatory sentencing law took effect in January 1977, but the rate since has been creeping upward, said chief assistant county prosecutor Dominick R. Carnovale. Publicity about the law ended long ago, Carnovale said, adding that judges unhappy over their loss of sentencing discretion have figured out ways to finesse the mandatory penalties.

James W. York, former commissioner of the Florida Department of Law Enforcement, said that the impact of that state's mandatory sentencing law for gun violators also has diminished since it was passed six years ago. But, York said, the more recently enacted mandatory minimum sentencing law for drug smugglers has been "very effective."

"The public in this state is fed up with the level of smuggling activity going on. So they are vocally supporting law enforcement resources to deal with it and chastizing those who don't use the law," York said.

York said he believes that mandatory minimum sentencing laws can work if the community considers the law's impact on the courts, prosecutors and the prisons. Otherwise, he said, ""you're doing nothing more than tinkering with the system."

In Pennsylvania, where mandatory minimum prison terms for gun offenses, repeat offenders and for violent crimes on public transit went into effect in June, the state is also undertaking a prison expansion and construction program.

"It doesn't make sense to say you're going to put people away unless you have a place to put them," said one state official.

The biggest concern among opponents of Initiative 9 is that mandatory sentencing proposals are politically attractive and immediately appealing to citizens concerned about crime. The arguments against the measure are not easy to explain -- compared to the proponents' simple demand to get tough on guns and drugs -- and the debate often comes down to an exchange of statistics about the experiences of states where such laws have already been adopted, the opponents say.

Once an initiative is on the ballot, it "puts the burden on the community to be informed" about the issues, said attorney Lorena Cabaniss, who works for Council member and mayoral candidate Charlene Drew Jarvis (D-Ward 6). Jarvis and the other candidates in the mayoral primary with Ray, Mayor Marion Barry and Patricia Roberts Harris, all oppose Initiative 9.

So far the campaign for and against Initiative 9 has been both low-budget and low-key. City records show that Citizens for Safer Streets, which was founded by Ray, has collected about $2,700, while Citizens for Sensible Sentencing, a community-group coalition organized this summer to oppose Initiative 9, has raised $700 since early August.

Citizens for Safer Streets plans to send letters to the 24,000 people who signed the ballot petition, urging them to get out and vote in favor of Initiative 9. But such plans are "all contingent on raising money," said the group's treasurer, attorney Ronald C. Jessamy.

Former D.C. Police Chief Burtell M. Jefferson recently left his post as manager of Ray's campaign to work full time on passage of the sentencing initiative as president of Citizens for Safer Streets.

Citizens for Sensible Sentencing has prepared a small handout which says "Thumbs down on Nine. It won't stop crime." The local office of the American Civil Liberties Union, a vocal opponent of the measure, has prepared a two-page educational pamphlet called "The Truth About Mandatory Sentencing."

The D.C. Chapter of the League of Women Voters has a "Study & Action" statement which ends -- after two pages of detailed discussion in fine print -- with the League's statement in opposition to Initiative 9.

The ACLU, in its pamphlet, says that even if citizens think crime in the District is a big problem, mandatory sentencing is "the wrong solution" because it will drain government money from other crime prevention programs, schools, job training and drug treatment centers.

"Tax dollars should be spent to support these programs, not to warehouse more people in prison," the pamphlet says. It notes that in addition to the ACLU, the D.C. Chapters of the League of Women Voters, the NAACP, the Urban League, the National Conference of Black Lawyers and the National Lawyers Guild all oppose the measure.

The popularity of mandatory sentencing laws -- whether they work or not -- was highlighted in a 1979 University of Michigan study of citizens in the Detroit metropolitan area.

In that study, not only did 90 percent of the citizens surveyed say they favored the law, but 65 percent also said they favored it even if it didn't help deter crime, according to criminologist Colin Loftin, who worked on the study.

"People think committing an offense with a gun is a serious offense and they have the sense that people are not being sentenced appropriately," Loftin said in a telephone interview, "so this kind of law is just in the eyes of the population."

Ray has said that he realizes that mandatory minimum sentencing is "only part of a larger attempt to solve the problems of criminals and their crimes" and he concedes that the "down side" to one study he cited is that it warns that such laws will crowd the prisons.

But, Ray says, "We have to do something about crime."

On Sept. 14, Washington's voters will decide whether mandatory minimum sentencing is what should be done.