MNF-I's methodology identifies a number of factors, necessarily subjective, that help analysts determine whether an attack or a death should be considered sectarian. Ethno-sectarian violence is defined as violence "conducted by one ethnic/religious group against another ethnic/religious group, where the primary motivation for the event is based on ethnic or religious reasons." MNF-I analysts consider the location of the attack -- whether it took place in a mixed area or a homogeneous one -- and the type of attack in order to determine ethnic or sectarian violence.
Interestingly, attacks against "same-sect civilians," U.S. forces, the Iraqi government or Iraqi security forces "are excluded and not defined as sectarian attacks." So even though Sunni insurgent groups loathe the Shiite-controlled government, insurgent attacks on it aren't considered sectarian violence.
Additionally, MNF-I calculates that the use of suicide vests, car bombs and IEDs strongly indicate Sunni perpetrators; and reasons that attacks using those methods on "medical centers, market places or religious symbols, mosques, religious gatherings, stores/restaurants, and housing areas" typically indicate sectarian violence, since those entities are primarily used by "one ethnic/sectarian group." MNF-I acknowledges that in these attacks "there may have been Sunnis killed or injured," and though it says it excludes "same-sect civilians" from the tally, these are counted as sectarian attacks.
For executions, murders and kidnappings -- situations in which sectarianism may be difficult to determine -- MNF-I says it uses "host nation" reporting in addition to its own. Many media and non-governmental organizations consider information on casualties released by the Iraqi ministries to be self-serving, misleading or contradictory.
Putting one rumor to rest: there is no consideration given to the placement of an entry wound on a murder suspect's head in the tabulation of sectarian violence, contrary to a Washington Post report earlier this month.