Analyses show that the 'most serious charge at arrest' may not accurately describe the actual offense of prosecution and that the 'offense may have occurred as a result of contact with the system, not prior to that contact. In addition, sociodemographic characteristics of persons recorded by the OBTS are established within and by the system and may provide unreliable measures of white and Hispanic offenders. Finally, OBTS data on prosecutors' reasons for not prosecuting are invalid because coded reasons have little relevance to actual reasons. These problems reflect generic problems inherent in attempts to codify and quantify procedures within people-processing organizations. Similar methodological problems can be found in medical and epidemiological data. Results suggest that such data cannot be read literally, but rather must be interpreted as describing the distribution of formal categories available to officials in the criminal justice system. 15 tables, figures, and 116 references.