As more police departments switch to the FBI’s National Incident-Based Reporting System (NIBRS), a look at data from one state reveals that discrepancies can arise due to a design flaw in NIBRS, the timing of arrests, and human factors.
The study, published in Crime & Delinquency, found that approximately 16% of cases incorrectly indicated in NIBRS whether arrests were made or summonses were issued by comparing NIBRS case statuses with data collected directly from the Massachusetts jurisdictions where the crimes occurred.
In addition to Emory University’s director of research analytics Alex Wagner and Criminal Justice Consultation and Research’s Daniel Bibel, Cross collaborated with them on the study.
Bibel, an expert in the NIBRS who oversaw the Massachusetts State Police Crime Reporting Unit for 27 years, assisted the research team in securing a random sample of cases for the NIJ-funded study that appeared in the journal Crime and Delinquency.
“This study compared NIBRS arrest data in a statewide sample with arrest and summons data on the same cases collected directly from law enforcement agencies (LEAs). NIBRS matched LEA data in 84.1% of cases. However, 5.8% of LEA arrests and 52.9% of LEA summons were false negatives, that is, they were incorrectly represented as not cleared by arrest in NIBRS,” according to researchers.
“False negatives were more likely when more than 1 day elapsed between incident and arrest and when the crimes were sexual assault or intimidation. False negatives were less likely in small LEAs (for summons) Recommendations are presented for improving accuracy.”