To women's groups and some law enforcement officials, the course of action in domestic violence cases is clear-cut. If somebody punches somebody on the street, they say, police know just what to do. So why should it be any different if the person being punched is a spouse?

"You would not swing on your boss or somebody in the Safeway because you'd be charged with assault and you'd be thrown in jail," said Dan Byrne, deputy director of the House of Ruth women's shelter.

Beginning this fall, under the District's new domestic violence law, a similar fate will befall those who physically assault their spouses or partners. The measure will require police to make arrests if they have "probable cause" to believe an assault or the threat of assault has occurred.

Authorities, citing the experience of other jurisdictions with such laws, expect the number of arrests in domestic abuse cases to skyrocket.

"We hope the word will get out -- and the word will get out -- that if you hit your spouse, you're going to jail or you're going to be dealt with severely," said Lt. David Sargent, spokesman for the D.C. police department's domestic violence task force, which is developing procedures for enforcing the law.

Proponents of the measure say it constitutes a long overdue crackdown on a serious crime. But critics, including some of those charged with enforcing the new law, say it will overburden police with arrests and reporting paperwork -- for cases that seldom result in prosecution anyway.

"It's a good law, but most of these cases are not going anywhere," said Detective David Israel, chief shop steward with the D.C. chapter of the Fraternal Order of Police.

Israel and several other police officers said domestic violence has never been a high priority as far as arrests go, in part because the department is already struggling to keep up with homicide and drug cases. But even when the arrests are made, they complained, the cases frequently get dropped, either because the complainants decide not to prosecute or because the prosecutors themselves don't pursue the case.

Women, Israel said, are usually reluctant to press charges against their husbands or partners, particularly if the man is the sole source of support in the family. When police intervene, he said, the woman is looking for protection "and the chance to work it out."

Supporters of the new law dispute this, saying women who suffer repeated physical abuse will take legal action, especially in communities where the courts take a strong prosecutorial stand. They are far more concerned about the prosecution end of the enforcement equation, particularly whether the U.S. Attorney's Office will move ahead with the domestic violence cases headed its way.

"Essentially, there has been no prosecution in the District of domestic assaults," said Mary Pat Brygger, executive director of the National Woman Abuse Prevention Program. "We're trying to get everybody in the system, not just the police, to see this as more than a personal family problem and to respond appropriately."

Brygger said the U.S. Attorney's Office has expressed concerns about the resources it may take to prosecute domestic abuse cases and whether the office will get cooperation from the victims.

"We've made information available to them about other communities where prosecutors have taken a strong prosecution stand," she said. "Between 70 to 80 percent of the victims will follow through and testify as witnesses."

U.S. Attorney Jay B. Stevens said his office regards domestic violence as a serious problem.

Determining whether a threat is a threat "may be a difficult judgment to make," Stevens said, citing one provision of the law. But it is "a misperception," he said, to think that domestic violence cases are a low priority in the federal courts.

"If we have the evidence to make the case, and if the complainant desires to proceed, we'll procecute those cases," Stevens said.

The mandatory arrest law, which was sponsored by D.C. Council member Hilda H.M. Mason (Statehood-At Large) and approved by the full council last month, will take effect in late September or early October after a 60-day congressional review period. Officers who investigate a domestic dispute will also be required to file a written report about the incident, including the disposition of the case.

The D.C. police task force is composed of police and court representatives as well as social service and community groups with an interest in the new measure. The panel, according to several members, is expected to recommend that the police department set up a pilot program to train officers for their expanded responsibilities.

Since 1987, the D.C. police department has had a policy that says officers "should" make arrests when they believe a domestic assault has occurred. Until recently, however, police officers usually opted to counsel the couple at the scene rather than arrest the batterer.

A 1988 study by the D.C. Coalition Against Domestic Violence, a victims' rights group, and the Women's Law and Public Policy Fellowship found that arrests were made in 5 percent of 300 domestic violence cases studied by those groups. Police that year made reports in 44 of the 18,264 calls the department received requesting assistance in domestic situations, according to the study, and arrests usually weren't made even when the victims' injuries were serious enough to require hospitalization.

The study helped prompt the mandatory arrest law and led to a new emphasis on enforcement. Recent statistics show that of 7,159 domestic calls received by police from Jan. 1 to May 20 of this year, officers filed 250 reports and made 150 arrests.

Eric Garrison, administrator of the District's Citizens' Complaint Center, whose mediation service handles nearly 300 spouse abuse complaints a month, said the problem will outlast the city's drug and homicide notoriety unless something is done.

"I'd characterize it as almost epidemic here in some communities," he said. "Not only do we have men who believe it's okay to hit women, but we have women and children who sometimes believe that it's inevitable that this happens."

Brygger and other victims' rights advocates say making an arrest is the most effective way to break the cycle of violence. They acknowledge that the mandatory arrest law will be burdensome on police and the courts at first, but say this will level off once authorities start prosecuting domestic violence cases.

Pointing to Minneapolis and Kansas City, Mo., jurisdictions that have been in the forefront of tougher domestic violence legislation, they say domestic assaults decrease dramatically, particularly when judges can order the batterer into a treatment program.

Closer to home, Alexandria, Baltimore and Newport News, Va., also have reduced the incidents of domestic violence by adopting stronger enforcement policies or laws.

Alexandria has a mandatory arrest policy. Since 1988, 14 percent of Alexandria's convicted spouse abusers were arrested again. The national rate for repeat arrests is 41 percent, according to the Bureau of Justice Statistics.

In Baltimore, which has a pro-arrest policy but no actual mandatory arrest law, "our caseload has grown by leaps and bounds," said Roni Young, director of the domestic violence unit for the state's attorney's office there. The office was so swamped at first with cases -- and ordered so many men into a treatment program and supervised probation -- that her domestic violence unit had to shut down temporarily.

But the message is getting through, she said, and many women have come forward to press charges. The office's conviction rate was running about 40 percent earlier this year.