Background checks save lives, says new research from the Johns Hopkins Center for Gun Policy and Research.

In 2007 the state of Missouri repealed a law that had required all handgun purchasers to get a license that verified they had passed a background check. The immediate aftermath of that law coming off the books was a sharp uptick in the state's murder rate.

According to a forthcoming study to be published in the Journal of Urban Health, Missouri's murder rate jumped 16 percent, with roughly 60 more murders committed each year from 2008 to 2012 compared with the period before the law's repeal.

Among the types of murder that spike when background checks aren't required are domestic-violence homicides. Though estimates vary, more than 40 percent of women murdered each year are killed by intimate partners, according to a study that appeared in the British medical journal The Lancet last year. More than half the women murdered each year are killed with firearms — and in nearly 75 percent of those deaths, the weapon is a handgun. Female victims of domestic abuse are five times more likely to be killed if their abuser owns a handgun.

An analysis of FBI data by the coalition Mayors Against Illegal Guns shows that in states where background checks are mandatory, 38 percent fewer women are killed by intimate partners each year. Some of the lowest female homicide rates in the country are found in states such as Illinois, Massachusetts and Hawaii, where background checks are required for all gun purchases, even for private transactions at places like gun shows.

Meanwhile, South Carolina, which does not mandate background checks between private parties, has the highest female homicide rate in the country. And, according to the Violence Policy Center, its rate of women killed by intimate partners is double the national average.

The map below shows both the states where background checks are required for sales at gun shows (indicated by the colored markers) and the female homicide rate (with those in darker blue having higher rates).