THE SITE-BASED MODEL CALLS FOR THE COLLECTION OF EXISTING COURT PROCESSING DATA ONSITE AT THE LOCAL CRIMINAL COURTS (NORMALLY ORGANIZED ON A COUNTY BASIS) INSTEAD OF USING CENTRALLY REPORTED AND STORED CASE PROCESSING DATA (NORMALLY KEPT BY THE ADMINISTRATIVE OFFICE OF THE STATE'S HIGHEST APPELLATE COURT). THIS APPROACH WAS USED TO STUDY A NUMBER OF QUESTIONS ABOUT THE POTENTIAL IMPACT OF PENAL CODE REFORM IN INDIANA. THE INDIANA REFORM, WHICH TOOK EFFECT IN OCTOBER 1977 WAS A COMPLETE REVISION OF THE SUBSTANTIVE AND PROCEDURAL CRIMINAL LAW, INCLUDING IMPLEMENTATION OF A FLAT-TIME, DEGREE-BASED SENTENCING STRUCTURE TO REPLACE THE MUCH CRITICIZED INDETERMINATE SCHEME. THE SAMPLING PROCEDURE USED WAS A SYSTEMATIC RANDOM SAMPLE OF ALL FELONY CASES FILED FOR A PARTICULAR YEAR WHICH ENDED IN CONVICTION; IN CASES WITH MULTIPLE DEFENDANTS, EACH WAS LISTED AS A SEPARATE CASE, AND WHERE A SINGLE INDIVIDUAL WAS CHARGED IN SUCCESSIVE CASES, THE DEFENDANT WAS LISTED ONLY ONCE. AFTER THE SAMPLE WAS CONSTRUCTED, FOUR SOURCES OF INFORMATION ON THE CASE WERE USED: COURT DOCKETS, COURT FILES, PRESENTENCE INVESTIGATIONS, AND PROSECUTOR'S FILES. SUBSTANTIAL DIFFERENCES WERE FOUND IN PROSECUTOR'S SCREENING PRACTICES. FOR EXAMPLE, IN ONE COUNTY WITH A POPULATION OF ABOUT 10,000, ALMOST 200 FELONIES WERE FILED, BUT ONLY 20 FELONY CONVICTIONS RESULTED; SCREENING OR BARGAINING OCCURRED AFTER ARRAIGNMENT, AND MANY GUILTY PLEAS RESULTED IN FINES. WIDE VARIATION WAS ALSO FOUND IN THE QUALITY OF ROUTINE RECORDKEEPING. IN SMALLER COUNTIES PARTICULARLY, DATA WERE OFTEN STORED IN A HAPHAZARD MANNER AND DATA WAS FREQUENTLY MISSING. HOWEVER, DESPITE THE FACT THE DIFFERENCES IN QUALITY OF DATA SOURCE BOTH WITHIN AND BETWEEN COURTS RAISE PROBLEMS OF DATA VALIDITY AND RELIABILITY, THE UNIQUE PROPERTIES OF SITE-BASED DATA ENHANCE CERTAIN KINDS OF ANALYSES OF CRIMINAL JUSTICE DECISIONMAKING. THE CRIMINAL JUSTICE THEORETICIAN CAN INVESTIGATE THE IMPACT OF DIFFERENCES IN COURT-SERVICE SUPPORT SYSTEMS ON SUCH VARIABLES AS CASE-FLOW AND CHARGING AND PUNISHMENT DECISIONS. THE DATA CAN ALSO BE VALUABLE AS A PLANNING AND MANAGEMENT TOOL. REFERENCES ARE CITED. (KBL)