IN 2009, ONE-FOURTH of the District’s 144 homicides were linked to abusive relationships. The following year, according to the advocacy group D.C. Safe, the number of domestic-violence homicides fell by half.

In Maryland, there has been a 41 percent drop in the number of homicides linked to domestic violence over the past three years.

The rate of violent crime overall has been declining, but not that fast. The dramatic drop in domestic-violence deaths in Maryland and the District is due largely to a simple but effective tool that helps identify women most at risk of being killed by their husbands or boyfriends. It is a tool that, if used nationwide, could save hundreds of the approximately 1,200 women killed every year by partners or former partners.

According to the Maryland Network Against Domestic Violence, the approach consists of a “user-friendly, 11-question screening tool” used by law enforcement officers and others who come into contact with victims of domestic violence.

Some of the questions are what you might expect: Has your husband or boyfriend ever used or threatened to use a weapon against you? Has he ever tried to choke you? (Although men are also victims of domestic violence, women are the victims in at least 85 percent of the cases.) Other questions, perhaps less obvious, include whether the man is unemployed and whether there is a child in the household who is not the biological offspring of the potential perpetrator.

As important as identifying women at heightened risk is offering immediate help, including counseling and emergency housing.

Fourteen states and the District use some form of the lethality assessment. Given the program’s success, that’s 36 states too few. Congress has a chance to help the program be adopted more widely when it reauthorizes the Violence Against Women Act (VAWA), which was passed in 1994 to raise awareness of and combat domestic violence and to provide federal support to state and local communities to assist victims. Sen. Patrick J. Leahy (D-Vt.), who is shepherding the reauthorization, is considering adding the lethality assessment to the list of programs that state and local entities may fund with VAWA dollars. Extending the life-saving benefits of the program to all of the nation’s at-risk women should be a priority.