Dahmann (1983) used an interrupted time-series design with comparison groups to study the effectiveness of the Hardcore Gang Investigations Unit in Los Angeles, California using data compiled between 1976 and 1980. Because there was limited data for juvenile cases, the analysis focused on the data accumulated from adult prosecutions. The study compared three groups:
- Pre-Hardcore No Program Group: this included cases prosecuted between 1976 and 1978, before Operation Hardcore began (Group 1).
- Post-Hardcore No Program Group: included cases prosecuted between 1979 and 1980 by regular trial attorneys and not in the Operation Hardcore Program (Group 2).
- Post-Hardcore Program Group: included cases that were prosecuted by Operation Hardcore attorneys (Treatment Group).
Data was collected in a three-step process, which began with identifying cases with criminal events (i.e., gang-related murder incidents), then identifying suspects, and finally, creating a list of suspects whose criminal charges had been accepted or rejected by the prosecution. Data collected from police and prosecutorial records included the characteristics of suspects, victims, and criminal justice handling. The study compared groups based on the type of disposition, the strength of the conviction, and outcome at sentencing.
Between 1976 and 1980 there were 526 incidents of homicide attributed to street gangs. These incidents involved a total of 1,016 suspects, of which 660 were identified by the police and 340 were charged by prosecutors. A total of 223 criminal cases were filed in response to the incidents. The suspects of these gang perpetrated homicide incidents were primarily male (less than 5 percent were female over the 5-year period). Approximately 20.3 percent of the suspects were under 18 years of age, 44.7 percent were between 18 and 21 years of age, and 35.0 percent were over 21. The majority of the suspects were Hispanic (64.5 percent), followed by Black (31.6 percent), White (2.7 percent), and Other (1.1. percent).
The study by Pyrooz, Wolfe, and Spahn (2010) further analyzed the data collected from the original study by Dahmann in 1983. This study examined the prosecutorial decisions that led to the rejection of gang-related homicide charges from Operation Hardcore between the years 1976-1980. The primary outcomes were to identify victim, suspect, and incident characteristics that were associated with the decisions not to pursue charges against a suspect, as well as what was the likelihood of lower case rejection for gang-related cases prosecuted by a specialized unit. Secondary outcomes included examining the effectiveness of the Hardcore Gang Investigations Unit and better understanding the roles that gangs play in the criminal justice system.
Researchers were able to access data across three distinct data sets: (1) victim based, (2) suspect based, and (3) incident based. They then merged this data into a suspect-referenced data file, where they used the unique incident identification number to match the incident to the suspect identification number. They excluded any cases that did not result in death, cases that had no death information, and cases where there was no suspect information. This left a total of 1,002 suspects. They also eliminated cases where no suspects were arrested. This left a total sample size of 614 suspects who were involved in gang-related homicides in Los Angeles between 1976 and 1980, and whose cases were sent to the District Attorney’s Office for a charging decision. A series of logistic regression models was used to analyze the data sets.