States that have stricter background-check laws for gun purchases have fewer school shootings, and some show reduced gun homicide rates overall.
A 2018 study published in BMJ looked at 154 school shootings from 2013 to 2015 and found that states with background-check policies had fewer such events. States that spent more money on education and mental health-care also had lower rates of school shootings.
Another study from 2015 found that a 1995 Connecticut law requiring gun buyers to get permits that involved background checks was associated with a 40% reduction in gun homicides.
By contrast, a study found that after Missouri repealed its permit-to-purchase law (which included a background-check requirement) in 2007, the change was associated with a 23% increase in gun homicides.
Research from the nonpartisan Rand Corporation estimates that universal background-check policies, which would mandate background checks for all firearm sales and transfers (including between private parties), could prevent 1,100 gun homicides per year.