The VLM file was created from the Supplementary Homicide Report (SHR) files collected by the Illinois Department of Law Enforcement and includes data on victim's characteristics; offender's characteristics; time, month, year, and jurisdiction of offense; circumstances; weapon; and victim-offender relationship. The VLM contains only one record per victim, whereas the SHR may have separate records for each known offender and thus more than one record for a murder victim. An investigation into data quality found no errors caused by SHR to VLM recoding, but did uncover possible errors and incomplete data in the SHR file. A subsequent check of the SHR data against the original police and sheriff's files found agreement in 75 percent of the cases. A more detailed 1981 audit revealed the following typical errors: (1) duplicate cases; (2) data discrepancy which can occur if someone dies in March as result of an attack in December; and (3) failure to designate whether homicides are murders or other types of homicides. The report describes the SHR to VLM recoding methods and differences between Chicago and non-Chicago race data in the SHR files caused by different reporting formats. In addition to the codebook, the document provides a supplementary homicide report form, tables, and maps of Illinois' counties and circuit courts.