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Standardizing the Display of IBR Data:
Weapon Variables

Data Collection and Quality Issues Associated with Weapon Variables

Weapons at a Glance

Segment? Offense
Required? For some offenses
Number of Entries? 3
Number of Coding Options? 17

Data Collection

Type Weapon/Force Involved is used to enter the type(s) of weapon(s) or force used by the offender(s) in committing certain offenses.  This data element is found in the Offense segment and is to be completed for the following offenses:

Murder and Nonnegligent Manslaughter Forcible Fondling
Negligent Homicide Robbery
Justifiable Homicide Aggravated Assault
Kidnapping/Abduction Simple Assault
Forcible Rape Extortion/Blackmail
Forcible Sodomy Weapon Law Violations
Sexual Assault With an Object

When one of these offenses occurs, up to three types of weapons/force can be entered.   Multiple weapons will exist if either one offender used multiple weapons, or if multiple offenders in the incident each used one or more weapons.  If the weapon is an automatic firearm, an "A" is added as a suffix to the code.  An automatic firearm is defined as any firearm which shoots, or is designed to shoot, more than one shot at a time by a single pull of the trigger without manual reloading.  There are 17 allowable entries:

Firearm (type not stated) Poison
Handgun Explosives
Rifle Fire/Incendiary Device
Shotgun Drugs/Narcotics/Sleeping Pills
Other Firearm Asphyxiation
Knife/Cutting Instrument Other
Blunt Object Unknown
Motor Vehicle None
Personal Weapons

When reporting the weapons used, select the most specific weapon-type listed, e.g., a revolver should be reported as Handgun rather than Firearm.  If a weapon was used that could be employed in several ways, choose the weapon-type that indicates how the weapon was used.  For example, if a bottle was used in the commission of a murder, report Blunt Object if the victim was beaten or Knife/Cutting Instrument if the victim was cut or stabbed.

Data Quality Issues

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Check that offenses include a weapon when required
bullet.gif (326 bytes) Check that offenses are correctly coded


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Check that offenses include a weapon when required
  • For the offenses listed above, a weapon type is required.

    The easiest way to check this is to run frequencies and review the numbers.  The following example determines whether Type of Weapon is being completed for homicide offenses. 

    We can see from the table above that there are 1,288 records for the homicide offenses.   Now if we look at the number records with at least one weapon reported, the numbers should match.

    The table shows that 1,288 records have a value for this conditionally required data field.  All records were coded correctly in that at least one weapon was recorded.   Any records with missing data in these fields should be identified by the originating agency identifier (ORI) and incident number, so that these incidents can be researched and corrected.

    View and download SPSS syntax to run this data quality check.
    Note: Please check that the variable names used in this syntax match the variable names in your data file.  If you need assistance, contact JRSA.

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Check that offenses are correctly coded
  • Simple assaults usually do not involve a weapon other than personal weapons - if a more serious weapon is involved, then this may be a miscoded aggravated assault.
  • Aggravated assaults involve a weapon - if personal weapons are reported and there is minor or no injury reported, this may be a miscoded simple assault.
  • If no weapons are reported and there is no injury reported, then this offense may be miscoded or the information is incomplete.  The exception to this will be when pretended weapons or weapons the offender claims to possess are not actually used by the offender.  In these situations, none would be the appropriate response.
  • Negligent manslaughter involving an automobile are considered traffic-related offenses and in most cases should not be included in NIBRS.

    A crosstabulation will show how assault offenses are coded.  In this example, only the first weapon category is displayed.  A thorough check would examine all three weapon variables.

    assault_weapon.jpg (63461 bytes)

    As the table shows, 3,405 of the aggravated assaults and 44,804 simple assaults involve no weapon.  To determine which is miscoded, the weapon or the offense type, we need to look at the injury sustained by the victim.

    It appears that the 'None' weapon code is incorrect for the aggravated assaults associated with an injury (1,607 offenses).  For the aggravated assault offenses with no injury and either no weapon or personal weapons, these offenses appear to be miscoded or are missing information.  Also, there are 278 offenses involving personal weapons or no weapon that are missing an injury.  These offenses may also be miscoded.

    The simple assaults appear to be coded correctly, with no major injury resulting from the use of personal weapons.

    Download SPSS syntax to perform this data quality check
    Note: Please check that the variable names used in this syntax match the variable names in your data file.  If you need assistance, contact JRSA.

    Now we need to look at negligent manslaughter offenses to ensure that there are no offenses with automobiles as weapons.

    neg_auto.jpg (48277 bytes)

    As the table shows, almost 50% of the negligent manslaughter offenses involve a motor vehicle and should not be included in this data file.  These incidents need to be corrected; using these data will inflate the numbers of negligent manslaughter.

    Download SPSS syntax to perform this data quality check
    Note: Please check that the variable names used in this syntax match the variable names in your data file.  If you need assistance, contact JRSA.

Coding Issues

  • Biological attacks are coded based on the type of biological agent used.  For deadly diseases, type of weapon will be Other.  However, depending on the biological agent used, Poison may be designated.
  • In forcible sex offenses, personal weapons are often indicated.  Despite the requirement of a weapon type entry, the definition of forcible sex offenses implies that some force is going to be used during the commission of the offense.  Submitting a weapon as being used in every forcible sex offense defeats the statistical value.  Therefore, weapons should be indicated only in the event that there are injuries sustained by the victim or where the offender actually strikes the victim.
  • Please be aware that when using Weapon Type variables in your analysis and multiple offenders or victims are involved, you cannot match individuals with weapons.