A New England Journal of Medicine study,
just out, entitled The Weapons That Kill Civilians — Deaths of Children and Noncombatants in Iraq, 2003–2008, claims that evidence indicates that execution-style killings have been the highest killer of non-combatants, not military operations or suicide bombings.
The journal based their findings on figures from Iraq Body Count, the internet database which seeks to compile accurate numbers of civilian deaths in Iraq.
From the report...
Armed violence, such as that in the ongoing conflict in Iraq, is a threat to global health.1 It causes serious injuries and deaths of civilians, makes orphans of children, traumatizes populations, and undermines the ability of communities to provide adequate medical care even as it dramatically increases health care needs. Moreover, indiscriminate or intentional harm to civilians violates humanitarian principles and basic human rights. Believing that a careful assessment of the effects of different kinds of weapons on civilians in Iraq was needed, we used the database of the Iraq Body Count (IBC), a nongovernmental organization that documents civilian violent deaths in Iraq,2 to determine the nature and effects of various weapons on civilians in Iraq. The patterns we found convince us that documenting the particular causes of violent civilian deaths during armed conflict is essential, both to prevent civilian harm and to monitor compliance with international humanitarian law.
Download the entire 4-page study. NEJM_4_16_09.pdf