Experimental Research in Criminal Justice


Professor James Byrne

Oct. 30 th 2014

The Classic experiment has three components:

1. independent and dependent variables

2. pretesting and post-testing

3. experimental and control groups created via random assignment( variation on a theme: double blind experiments where neither the researcher or the subjects knows who is in experimental and control group)

The Minneapolis Domestic Violence

Experiment: examined the short term impact of mandatory arrest( compared to counseling, and business as usual) in misdemeanor DV cases

The Kansas City Preventive Patrol

Experiment: impact of police on crime, fear, and arrests


Random assignment to one of 3 conditions--control beats (normal level of preventive patrol);proactive( 2x level of preventive patrol); reactive beats( no preventive patrol)

The Newark Foot Patrol Experiment: impact of foot patrol on crime, fear, and arrests. Random assignment to foot patrol vs motorized patrol.

1. Misapplication of treatment( e.g.

Minneapolis Experiment)

2. No difference in intervention between treatment and control groups( Newark Foot


3. External Validity: the experiment does not work in real world( boutique programs; research rich interventions)

 1

. History: outside events that could also explain findings( e.g. research in 70’s on impact of laws to reduce drunk driving)

2. Maturation: people change: example-age and binge drinking

3. Testing: subjects become sensitive to responses exampledrinking/drug use surveys( pre-post)

4. Instrumentation: changes in measurement over time ( example-hate crime)

5. Statistical Regression: selecting subjects with extreme scores on a dependent variable, such as chronic offenders.

6.Selection Bias: picking good risks example- drug courts, bail research

7.Experimental Mortality: Dallas Women in Policing Study; boot camp

8. Diffusion of Tx( targeted community policing) and Compensatory Tx(

Kansas City Ex


1. Sample Size: Rand Study of ISP in 14 locations

2. Target group selection ( e.g. research study on certainty of incarceration by Weisburd; ISP refusals at two sites)

3. Lack of researcher control over random assignment: Minneapolis Experiment

4. After the fact random assignment: Project

Hope in Hawaii