To better understand the efficacy of cold-case investigations, this study was designed to address the following objectives:
- Assess current practices in cold-case investigations and agency policies and procedures and determine which are most effective in solving cold cases.
- Determine which types of cases are most likely to be solved, and develop models, based on case characteristics, for prioritizing cold-case investigations.
To assess the current practices in cold-case investigations, this study utilized a national online survey of law enforcement agencies (Cold Case Survey Data, n = 1,051) to document the range of ways in which cold-case work is conducted and assess how this organization affects cold-case clearance rates. In November 2008, the chiefs of police in the sample were sent a letter explaining the purpose of the survey and inviting them to participate. Potential respondents were directed to the web-based survey instrument through a provided web address. Three separate mails were made. The first mailing went to all 5,000 potential respondents. Two weeks later, letters were mailed to the 4,919 respondents who had not yet completed the survey. Two weeks after the second letter was sent, letters were mailed to the 4,570 respondents who had not yet completed the survey. The survey was taken down from the web in February 2009.
To determine the types of cold cases that were most likely to be solved, researchers used the results from the national survey to identify four jurisdictions that conduct large numbers of cold-case investigations. Researchers chose three jurisdictions that conducted a large number of cold-case homicide investigations: the District of Columbia, Baltimore, Maryland, and Dallas, Texas (Cold Case Homicide Data, n = 429). To these three sites, researchers added Denver, Colorado, (Cold Case Sexual Assault Data, n = 105) because it had received a Department of Justice grant to conduct testing of DNA material in sexual assault cold cases. At all four sites, cold cases were examined for seven categories of data including victim's characteristics, crime context, motivation, human capital, physical evidence, basis for cold-case investigations and cold-case actions.
The sample for the Cold Case Survey Data (n = 1,051) was drawn from a Bureau of Justice Statistics (BJS) database of chiefs of police and sheriffs. The database was comprised of 15,884 chiefs of police from all police departments in the United States, including Native American tribal police departments. A stratified sample of 5,000 agencies was drawn from the database. The resulting sample of 5,000 included Native American tribal police departments (n = 44) and all other departments with more than 100 full-time sworn officers (n = 997). The balance of the sample (n = 3,959) was comprised of police departments in the following size categories: 1,886 from departments with zero to 25 full-time sworn officers; 1,000 from departments with 26 to 50 full-time sworn officers; 707 from departments with 51 to 75 full-time sworn officers; and 366 from departments with 76 to 99 full-time sworn officers.
The results from the national survey were used to select sites for an analysis of case files. To ensure that researchers could obtain a large number of cases for analysis, only sites that reported conducting in excess of 50 cold-case investigations per year were considered. There were a dozen agencies that reported conducting more than 50 cold-case investigations per year; from these researchers selected the District of Columbia, Baltimore, and Dallas for analysis of cold-case homicide investigations (Cold Case Homicide Data) based on the additional considerations of travel distance, relationships with departments and feasibility. None of the three homicide case sites had computer files that were suitable for sampling cases. Further, cases in which a cold-case investigation had been conducted were mixed in with other homicide files, with no special notations on the case folder that indicated that a cold-case investigation had been undertaken. Therefore, at all three sites, researchers had to rely on cold-case investigators to create the sample. In all, 189 homicide cases were sampled in the District of Columbia, 113 in Dallas, and 127 in Baltimore. In each of the homicide sites, roughly half of the cases had been solved and half remained unsolved.
Denver was selected for the analysis of sexual assault cold-cases (Cold Case Sexual Assault Data) because it had received a Department of Justice (DOJ) grant to conduct testing of DNA material in sexual-assault cold cases. The Denver sample consisted of cases in which a DNA match had been made.
The universe for the Cold Case Survey Data is the police chiefs of all police agencies in the United States in November 2008. The universe for the Cold Case Homicide Data includes all cold-case homicide investigations in the District of Columbia, Baltimore, Maryland, and Dallas, Texas between 2008 and 2009. The universe for the Cold Case Sexual Assault Data includes all cold-case sexual assault cases with a DNA match in Denver, Colorado between 2008 and 2009.
Cold Case Sexual Assault Data: Sexual Assault case
Cold Case Homicide Data: Homicide case
Cold Case Survey Data: Police Department
administrative records data
The Cold Case Survey Data (n = 1,051) includes 223 variables on agency characteristics, factors contributing to the re-opening of cases, types and clearance rates of cold cases worked in the past year, existence of a dedicated cold case unit and caseload, institutional supports, and supports affecting cold-case investigation decisions and clearances.
The Cold Case Homicide Data (n = 429, 62 variables) and the Cold Case Sexual Assault Data (n = 105, 71 variables) contain information spanning the following 7 data categories, with slight differences based on crime type:
- Victim's Characteristics: age, gender, race, known gang member, known drug dealer, known drug user, known prostitute;
- Crime Context: time between crime and police arrival, location of body, struggle preceded death, method of death;
- Motivation: drug feud, theft, personal or emotional, gang feud, sexual assault;
- Human Capital: prime suspect identified, prime suspect interviewed, prime suspect arrested and released, eyewitness identified, other witnesses identified;
- Physical Evidence: weapon recovered, casings recovered, slugs recovered, prints recovered, identified via prints, suspect's DNA tested, suspect identified via DNA;
- Basis for Cold-Case Investigations: elapsed time, family inquiry, new physical evidence, new testing methods or untested evidence, media inquiry, new information from witness, suspect came forward; and
- Cold-Case Actions: tested physical evidence, reinterviewed witnesses, interviewed additional witnesses, identified new theory or suspect, pursued outstanding leads, checked investigative database, conducted lineup.
For the Cold Case Survey Data, of the 5,000 surveys mailed out, 1,051 were completed for a response rate of about 20 percent.