The purpose of the study was to estimate the rate at which
defendants are wrongly convicted and to identify case attributes associated with such wrongful convictions.
For the 634 criminal cases (and 715 convictions) eligible for this study, Urban Institute (UI) researchers collected three types of data from three separate sources: (1) Information on the physical evidence collected, submitted, and tested during the original investigation and the post-conviction DNA testing results (collected from the Virginia Department of Forensic Science (DFS) files); (2) Information on the original investigation, case processing, and disposition, including suspect and victim demographics (collected primarily from DFS but supplemented by visits to three Virginia county courthouses -- Alexandria, Arlington, and Fairfax); and (3) County-level sociodemographic and crime data from the 1970s and 1980s, collected from the COUNTY STATISTICS FILE 1 (CO-STAT): [UNITED STATES] (ICPSR 8314).
From March 2009 to August 2011, teams of four to six UI researchers conducted ten two-day site visits to the VA DFS laboratory in Richmond to review eligible cases after post-conviction DNA testing had been completed. When test results were delivered to DFS but prior to UI's visits, DFS staff designated cases as "Red" or "Green" depending on the results of the DNA analysis. Red cases were those containing exculpatory DNA testing results, meaning that at least one convicted offender was eliminated as a contributor of DNA found on questioned evidence. Green cases were those containing either inculpatory DNA testing results, meaning a convicted offender could not be eliminated as a contributor of DNA found on questioned evidence, or indeterminate DNA testing results, for all convicted offenders.
UI researchers established a detailed method of coding DNA testing outcomes at the convicted offender level and identifying the four possible outcomes of post-conviction DNA testing (indeterminate, inculpatory, exculpatory but insufficient for exoneration, and exculpatory supportive of exoneration). UI coding staff was trained on the proper use of the coding instruments and on the types of forensic analyses conducted at the time of the original investigation. After cases were coded, UI researchers conducted three types of quality control reviews: (1) a complete review of all cases that were coded during the first two site visits (after which the coding database was revised); (2) a complete review of cases that were randomly selected by DFS; and (3) a partial review (during the final site visit) of cases that were missing data for key forensic variables. All quality control reviews were conducted on-site with all DFS case file information available and by someone other than the original coder. Additionally, whenever DFS initiated further DNA testing and/or DNA testing results changed, that case was recoded. During the data-cleaning process, automated quality checks were performed to identify any variables that were in conflict with one another. Finally, at the end of the project, DFS staff reviewed all cases that UI coded as supporting exoneration.
After DFS data collection was completed in August 2011, a review of the data confirmed that the complete data were generally limited to basic case information and data on forensic test results. Data on important nonforensic case characteristics (e.g., type of counsel, trial or plea, sentence) were not present in enough cases to allow statistical tests of association between those variables and sample outcome designation. UI researchers undertook a pilot review of case data available at three local circuit courts -- the City of Alexandria, Arlington County, and Fairfax County. The three-court pilot study revealed that the court records included substantial case characteristics that were not widely available in the DFS case files. However, for technical reasons the research contract could not be extended to allow visits to the 94 counties with a convicted offender in this dataset.
To supplement the data collected from the DFS files and three-court pilot, the research team downloaded the COUNTY STATISTICS FILE 1 (CO-STAT): [UNITED STATES] (ICPSR 8314) for Virginia. The purpose of collecting these data was to identify any jurisdiction-specific variables that could potentially affect the case investigation and final disposition. The dates for each county variable ranged from 1977 to 1981.
The study examines cohort of 634 criminal cases (resulting in 715 convictions) of sexual assault and/or homicide dating from 1973 to 1988 in the state of Virginia. Of the cases originally reviewed (more than 534,000), approximately 3,000 had retained physical evidence; in 2,100 of those cases a suspect was identified; and 740 cases had at least one
suspect convicted of a felony. Of those, 634 cases with 715 convictions (62 cases had multiple suspects) were NIJ eligible based on crime type (homicide, sexual assault) and a conviction.
All sexual assault or homicide cases where there was a conviction and physical evidence was retained in Virginia between 1973 and 1988.
Court records available at three local circuit courts -- the City of Alexandria, Arlington County, and Fairfax County
Virginia Department of Forensic Science files
COUNTY STATISTICS FILE 1 (CO-STAT): [UNITED STATES] (ICPSR 8314)
administrative records data
The study contains 121 variables including; administrative variables, post-conviction DNA testing variables, pre-conviction forensic testing variables, case characteristics, convicted offender and victim demographics, and conviction county characteristics.