Kevin N. Cooper, 26, of Glen Burnie, Md., has just been sentenced to six months in jail and 500 hours of community service for drunk driving and the manslaughter deaths of five members of a Montgomery County family last Christmas Eve. Cooper, noted Carroll County Circuit Judge Donald Gilmore, is not a hardened criminal. So Gilmore sentenced Cooper to spend his time in the slammer in a work-release program that will let him out on weekdays.

The official cost to Kevin Cooper of his excesses--he admitted drinking seven beers at an office Christmas party before taking to the road--amounts to one tough year between the accident and the sentencing plus another six months in jail and the equivalent of slightly more than three months in community service. Less than two years of his life will be marked up on his side of the ledger. But to Martha Proctor of Clarksburg, who was taking her family to a Christmas pageant, the ledger will bear the names of two sons, ages 23 and 14, and three grandchildren, ages 3 years, 19 months and 5 weeks.

This is not exactly punishment that fits the crime.

In less than two years, the public sentiment in this country has gone from malignant tolerance of drunk driving to widespread support for tougher laws and sentencing against drunk drivers. Two years ago, Rep. Michael Barnes (D-Md.), who has been in the vanguard of reform efforts, called a press conference to announce he was introducing a drunk driving bill. The press, Barnes recalls, showed "zero interest."

But victims and relatives of victims who formed groups such as Remove Intoxicated Drivers (RID), Mothers Against Drunk Drivers, (MADD) and Students Against Drunk Drivers (SADD), in a truly extraordinary effort, have focused national awareness on the fact that drunk drivers kill 25,000 people a year, including 5,000 teen-agers, and that something can be done to reduce the carnage.

They have captured the interest of the White House, private businesses, the media, police departments, state governors, judges and lawmakers. Today, Barnes sits on a national commission appointed by President Reagan after more than 300 members of Congress petitioned Reagan to take a leadership role in the reform movement.

A new federal law requires states to have mandatory jail sentences for people convicted of drunk driving in order to receive additional Highway Safety Act funds. In Maryland, 16 laws have been passed in the past two years in an effort to reduce drunk driving. Last September, a Virginia man was convicted of three counts of second-degree murder, rather than the lighter charge of manslaughter, in an alcohol-related accident that killed three people.

Tom Sexton is MADD's Maryland state representative, whose son was killed by a drunk driver later fined $200. He sees the Cooper sentencing as "a classic example of why we have the problem we do . . . . Killing five innocent children with whole lives ahead of them, if you're not going to spend a substantial amount of time in jail for that, do we deserve to put anybody in jail?"

"I think what this case demonstrates is that we can pass all the laws that have been suggested . . . but what is really at issue is the need to change people's attitudes," says Barnes. "It's a national attitude that drunk driving is an accident and not really a crime.

"I think the person who drinks and drives and looks at this sentence is not going to get a message of deterrence from it."

Judge Gilmore would not discuss the Cooper sentencing, saying it was a pending case. He calls drunk driving "the second biggest problem next to drug trafficking we have in the country today."

He points to zoning laws that force people to drive to taverns and the failure of the law to hold responsible people who serve too many drinks. "We're all guilty of neglect. You can't just bring the whole thing down on one individual suddenly."

Despite the interest and reforms of the past two years, the sad reality is that on the road and in the courtroom the crime and the punishment haven't changed that much. Five people were killed by someone who drank too much and the price he is paying is six months in jail. This is the kind of sentence that galvanized relatives and friends to reform the laws in the first place. That it can happen today is a measure of how complex the problem is and how much remains to be done.