PLYMOUTH, MICH. -- Ronald Harmelin, former Air Force honor guard, pool hustler and cocaine addict, spends his days shelving books in the library at the state prison here, his nights watching television in a 10 1/2-by-7 1/2-foot cell.

If the state of Michigan has its way, Harmelin will remain in prison for the rest of his life.

His crime: possession of 672.5 grams -- about a pound and a half -- of pure cocaine. When police stopped him in 1986 for running a red light and discovered the drugs in the trunk of his car, Harmelin had no history of violence. He had no criminal record.

A 1978 Michigan law requires that those convicted of possessing more than 650 grams of cocaine be sentenced to life without the possibility of parole. The penalty, the harshest in the country, is the same as that for first-degree murder. Michigan has no death penalty.

A growing number of states and the federal government have turned to lengthy mandatory minimum sentences as a means of combating the drug problem or punishing other serious crimes. Today, in a case that could determine the future of such efforts, the Supreme Court will consider Harmelin's argument that his sentence violates the constitutional ban on "cruel and unusual punishments."

As a matter of social policy, the Harmelin case raises questions about the purposes of incarcerating criminals, the role -- if any -- of rehabilitation and the degree to which sentences must take individual moral culpability into account.

As a question of law, it presents the court with the need to address the scope of the Eighth Amendment prohibition on "cruel and unusual punishments" and the meaning of a 1983 case in which the court ruled that criminal sentences must be "proportionate" to the crime.

Harmelin, now 45, pleads for a second chance, arguing that he "wasn't intentionally trying to harm anybody," failed to "realize the threat I was to society" and wants the opportunity to make amends.

"I'm not saying I shouldn't be punished," Harmelin, a soft-spoken man in an olive drab prison uniform, said in an interview. "I should be punished, and I'm being punished. But the sentence doesn't fit the crime, not for what I did."

Prosecutors, supported by the Bush administration, contend that the menace drugs pose to society makes Harmelin's life sentence appropriate and certainly makes it constitutional.

"Drug-trafficking is one of the greatest and gravest dangers facing the United States," they told the Supreme Court in a brief. "Michigan's mandatory penalty for those dealing in large quantities of drugs is not grossly disproportionate as a weapon in the national war on drugs."

Harmelin, they note, was caught near a suburban Detroit motel with the tools of the drug dealer's trade: pure cocaine worth between $67,000 and $100,000, 10 small packets of the drug, assorted pills, marijuana, a beeper, a coded address book, a gun and $2,900 in cash.

"Many people will raise that 'I'm a first offender and I should have another chance' " argument, said Oakland County Prosecuting Attorney Richard Thompson, who will argue on the state's behalf. "My retort to that is it is the first time you got caught. . . . You don't come upon a pound and a half of cocaine by accident."

Comparing Harmelin's prison sentence with what he would have gotten for premeditated murder, Thompson said, "In some respects, drug dealers are worse than murderers. A murderer in most instances will kill one person. A drug dealer destroys life after life and spurs other drug dealers to do the same thing."

Although his lawyer refused to allow him to discuss his crime in this interview, Harmelin has acknowledged to the Detroit News that he was selling cocaine in half- and quarter-gram packages. Thompson said he would consider Harmelin "at least a mid-level dealer."

Since the law was adopted 12 years ago, 123 people have been sentenced to life without parole, 56 of them in 1989. As of a year ago, half of those sentenced under the law had no prior convictions, according to a Detroit Free Press study. Although the Michigan courts have upheld the law, even its author -- now a criminal defense lawyer -- has expressed misgivings about its impact.

The future of Harmelin and others sentenced under the law will hinge on the court's interpretation of its 1983 ruling in Solem v. Helm, in which the justices overturned a life sentence without parole for a repeat offender (six nonviolent felonies) convicted of writing a worthless $100 check. The court, voting 5 to 4, said the punishment was "significantly disproportionate," and therefore unconstitutional, considering the gravity of the offense, the sentence imposed for other crimes in the state and the sentence

imposed for the same crime elsewhere.

The dissenters said that analysis might be justified in "extraordinary cases -- such as a life sentence for overtime parking." But they said that "in all other cases" the court should not be in the business of second-guessing legislative decisions about appropriate punishment.

Prosecutors argue that Harmelin's sentence passes the Solem test, but they also suggest that Solem be overruled, a step some attorneys and Supreme Court analysts think the court might want to take.

In attacking his sentence, Harmelin's attorney, Carla J. Johnson, argued that the constitutional flaw in the Michigan statute is that, unlike any crime but premeditated murder, it prevents judges from taking individual circumstances into account -- that Harmelin had no record, was not violent and has the potential to be rehabilitated.

She noted that only one other state, Alabama, mandates life without parole for possession -- and that is for 10 kilograms of cocaine -- nearly 15 times what Harmelin possessed. Under federal sentencing guidelines, Johnson said, Harmelin's "worst-case scenario" would be a prison term just over 10 years.

Johnson said that while the law was designed to punish "drug kingpins," it has caught what Harmelin calls "idiots like myself" -- low-level drug couriers. Bigger traffickers are prosecuted by the federal government, and subjected to shorter sentences.

"I'm not a major drug trafficker," Harmelin said. "I'm just a poor slob who was doing cocaine at the time. Everybody I've met that's been sentenced under this law, they're not drug kingpins. They're just regular guys like myself who just got . . . tricked into doing something, doing a favor for somebody or trying to pay off a debt to somebody by making a run."

The Free Press study supported his argument, concluding that the law "has mostly snared lower-echelon traffickers and has failed to contain the commerce of large amounts of drugs in the state."

The newspaper found that a 50-year-old grandmother with no criminal record was among those snared. She was arrested at the Lansing airport when she picked up a family friend who had 30 pounds of cocaine in his suitcase.

Prosecutor Thompson said the law "was not aimed at the drug kingpin" but "at the entire supply network," including couriers like Harmelin. "Other states are beginning to see the light," he said. "Their penalties are getting tougher and tougher."

Possession of 670 grams of cocaine would be punished by a maximum of four years in Maryland, 10 in Virginia and one in the District, according to the American Civil Liberties Union. Eleven states permit sentences of up to life, but with the possibility of parole, although some have mandatory minimums of up to 30 years, according to Thompson.

Solicitor General Kenneth W. Starr, defending the Michigan law, told the court it is "not radically different" from punishments imposed in other states for distribution or possession with intent to distribute.

At the time of his arrest, Harmelin was the night manager at a billiard parlor, earning $500 to $800 a week playing pool. Now, as prisoner 188131, he said, "Every morning when I wake up I have to sit down and try to find reasons to go on. . . . You sit around and listen to the guys next to you talk about when they're out or when they're up in front of the parole board, and you want to feel good for them, but the jealousy and the envy . . . they just start messing with your head."

Thompson said he has little sympathy. "This is a war on drugs," he said. "If there's going to be a casualty, I'd rather have that casualty be Ronald Harmelin or someone of his ilk than the children, born and unborn, that he is victimizing."