Cooper explained that a decline in the national homicide rate and local crime prevention efforts may have helped.
One hundred people died in domestic violence murders in 2009 compared to 131 in 2008. Sixty-one of the victims were women. The murders were committed by 79 male offenders and 21 females.
It's the second year Cooper's office has released figures from data reported to the State Bureau of Investigation.
Cooper said the decline may reflect early FBI statistics showing the U.S. murder rate fell last year. He also pointed to efforts such as those in High Point and Pitt County designed to prevent domestic violence.