Dr. Cohen's research analyzes many aspects of crime and criminal justice policy, including demographic trends in crime and prison populations, patterns of individual criminal careers, and incapacitative effects of incarceration. Recently, her work has focused on various aspects of illegal drug use and its relationship to violent offending, the increasingly important role of firearms in youthful violence, and investigations of the effectiveness of policing and housing strategies in reducing violence.
Dr. Cohen has contributed to the work of several panels convened by the National Research Council to examine research on deterrence and incapacitation, sentencing policy, patterns of offending during criminal careers, and the understanding and control of violent behavior. She has served on the editorial boards of Criminology, Law and Society Review, Journal of Quantitative Criminology, and as Associate Editor of Management Sciences, Evaluation Review, and Criminal Justice and Behavior.
“Neighborhood Socioeconomic Disadvantage and the Shape of the Age-Crime Curve” (with Anthony Fabio, Chuan (Charlotte) Tu, and Rolf Loeber). American Journal of Public Health, 2011.
“Linking the Crime and Arrest Processes to Measure Variations in Individual Arrest Risk per Crime (Q)” (with Alfred Blumstein, Alex R. Piquero and Christy A. Visher). Journal of Quantitative Criminology 26:533-548, 2010.
“Exploring Differences in Estimates of Visits to Emergency Rooms for Injuries from Assaults Using the NCVS and NHAMCS” (with James P. Lynch). In JP Lynch and L Addington (eds.) Understanding Crime Statistics: Revisiting the Divergence between the UCR and NCVS (New York City, NY: Cambridge University Press), 2007.
“An Ecological Study of the Location of Gang Set Space” (with George Tita), Social Problems 52(2): 272-299, 2005.
“Impact of Police Raids at Nuisance Bars on Illegal Drug Dealing: Estimating Intervention Effects in Varying Risk Settings” (with Piyusha Singh and Wilpen Gorr), Criminology 41(2): 257-292, 2003.
“Measuring Spatial Diffusion of Shots Fired Activity Across City Neighborhoods” (with George Tita) in Michael F. Goodchild and Donald G. Janelle (eds.) Spatially Integrated Social Science ( New York: Oxford University Press), 2003.
“Policing Crime Guns” (with Jens Ludwig) in Jens Ludwig and Philip J. Cook (eds.) Evaluating Gun Policy: Effects on Crime and Violence (Washington, DC: The Brookings Institution), 2003.
"Spatial Analyses of Crime" (with Luc Anselin, David Cook, Wilpen Gorr, and George Tita) in Criminal Justice 2000, Vol 4, Measurement and Analysis of Crime and Justice (Washington, DC: National Institute of Justice, US Department of Justice), 2000.
"Diffusion in Homicide: Exploring a General Method for Detecting Spatial Diffusion Processes" (with George Tita) Journal of Quantitative Criminology, Vol. 15, No.4, pp. 451-494, 1999.
"Gun Injury and Mortality: The Delinquent Background of its Juvenile Victims" (with R. Loeber, M. deLamatre, G. Tita, M. Stouthamer-Loeber, and D.P. Farrington) Violence and Victims, Vol. 14, No. 4, pp. 339-351, 1999.
"The Role of Drug Markets and Gangs in Local Homicide Rates" (with Daniel Cork, John Engberg, and George Tita), Homicide Studies, Vol. 2, No. 3, pp. 241-262, 1998.
"Hierarchical Bayesian Analysis of Arrest Rates" (with Daniel Nagin, Lawrence Wasserman, and Garrick Wallstrom); JASA, Vol. 93, No. 444, 1998.
"Relationship Between the Offending Frequency (l) of Imprisoned and Free Offenders" (with Jose A. Canela-Cacho and Alfred Blumstein); Criminology, Vol. 35, No. 1, pp. 133-175, 1997.
"Incarceration and Violent Crime: 1965-1988" (with J. Canela-Cacho). In A.J. Reiss Jr. and J. Roth (eds.) Understanding and Preventing Violence, Vol IV. Report of Panel on the Understanding and Control of Violent Behavior, National Research Council, National Academy of Sciences. Washington, D.C.: National Academy Press, 1994.
"Filtered Sampling from Populations with Heterogeneous Event Frequencies" (with A. Blumstein and J. Canela-Cacho) Management Science 39 (7): 886-899, 1993.
"Trend and Deviation in Crime Rates: A Comparison of UCR and NCS Data for Burglary and Robbery" (with A. Blumstein and R. Rosenfeld) Criminology Vol. 29, No. 2, pp. 237-263, 1991. "Deterrent Effects of the Police on Crime: A Replication and Theoretical Extension" (with R. J. Sampson) Law and Society Review, Vol. 22, 1988.
"Specialization and Seriousness During Adult Criminal Careers" (with Alfred Blumstein, Somnath Das, and Soumyo Moitra); Journal of Quantitaive Criminology Vol. 4, pp. 303-345, 1988.
"Characterizing Criminal Careers" (with Alfred Blumstein); Science Vol. 238, No. 4818, August 28, 1987.
"Selective Incapacitation: An Assessment," University of Illinois Law Review, Vol. 1984, No. 2, 1984.
"Incapacitation as a Strategy for Crime Control: Possibilities and Pitfalls," in M. Tonry and N. Morris, eds. Crime and Justice, Vol. 5. Chicago: University of Chicago Press, 1983.
Bachelor's and Master's degrees from the University of Pittsburgh
PhD, Carnegie Mellon University
Empirical Calibration of Time Series Monitoring Methods Using Receiver Operating Characteristic Curves
Time series monitoring methods, such as the Brown and Trigg methods, have the purpose of detecting pattern breaks in time series data reliably and in a timely fashion. Traditionally, researchers have used the average run length statistic (ARL) on results from generated signal occurrences in simulated time series data to calibrate and evaluate these methods, with a focus on timeliness of signal detection. This paper investigates the receiver operating characteristic (ROC) framework, well-known in the diagnostic decision making literature, as an alternative to ARL analysis for time series monitoring methods. ROC analysis traditionally uses real data to address the inherent tradeoff in signal detection between the true and false positive rates when varying control limits. We illustrate ROC analysis using time series data on crime at the patrol district level in two cities and use the concept of Pareto frontier ROC curves and reverse functions for methods such as Brown's and Trigg's that have parameters affecting signal-detection performance. We compare the Brown and Trigg methods to three benchmark methods, including one commonly used in practice. The Brown and Trigg methods collapse to the same simple method on the Pareto frontier and dominate the benchmark methods under most conditions. The worst method is the one commonly used in practice.(Download)
Exploring Differences in Estimates of Visits to Emergency Rooms for Injuries from Assaults Using the NCVS and NHAMCS
Researchers seeking to provide a better understanding of crime statistics tend to compare survey-based statistics such as the NCVS with data from police administrative series like the UCR. Because these two types of data collections systems are so different, simple direct comparisons are of little value regarding limitations inherent to a particular data collection system. This chapter explores the NCVS data using a different perspective that compares data from the national crime survey of population with those from a national survey of establishments-the National Hospital Ambulatory Care Survey (NHAMCS). This comparison provides an understanding of how the design, instrumentation and procedures of the NCVS may influence estimates of interpersonal violence, particularly that component of violence resulting in injuries treated in hospital emergency rooms. The estimates of emergency room visits for injuries due to violence obtained from the NCVS are considerably smaller than those from the NHAMCS. The analyses include a series of adjustments to these estimates that explore the role of features specific to each survey in the observed differences. The household sampling frame employed in the NCVS receives special attention as a potential source of the observed differences. Investigating this source of divergence is particularly important, since many of our major social indicators on the economy and participation in government programs depend upon household surveys. If some population groups are under-represented in the household sampling frame used in Census surveys, and this under-coverage results in underestimates of violence, this finding could have implications for the use of the household frame to estimate the magnitude of other problems that disproportionately affect marginal populations, such as unemployment, poverty, drug abuse and poor health status. The first section of this paper describes the two surveys, but principally the NHAMCS, since the NCVS is described extensively in Chapter 2. The second section presents the unadjusted estimates of the rate of emergency room visits due to violent crime from the two surveys. The third section outlines a series of potential explanations for the observed rate differences and the last section includes a series of adjustments to the rates designed to test the plausibility of the various explanations.(Download)
Leading Indicators and Spatial Interactions: A Crime Forecasting Model for Proactive Police Deployment
Based on crime attractor and displacement theories of environmental criminology, this paper specifies a leading indicator model for forecasting serious property and violent crimes. The model, intended for support of tactical deployment of police resources, is at the micro-level scale; namely, one-month-ahead forecasts over a grid system of 104 square grid cells 4,000 feet on a side (with approximately 100 blocks per grid cell). The leading indicators are selected lesser crimes and incivilities entering the model in two ways: 1) as time lags within grid cells and 2) time and space lags averaged over contiguous grid cells of observation grid cells. The validation case study uses 1.3 million police records including 16 individual crime types from Pittsburgh, Pennsylvania aggregated over the grid system for a 96 month period ending in December 1998. The study uses the rolling-horizon forecast experimental design with forecasts made over the 36 month period ending in December 1998, yielding 3,774 forecast errors per forecast model.(Download)
Estimation of Crime Seasonality: A Cross-Sectional Extension to Time Series Classical Decomposition
Reliable estimates of crime seasonality are valuable for law enforcement and crime prevention. Seasonality affects many police decisions from long-term reallocation of uniformed officers across precincts to short-term targeting of patrols for hot spots and serial criminals. This paper shows that crime seasonality is a small-scale, neighborhood-level phenomenon. In contrast, the vast literature on crime seasonality has almost exclusively examined crime data aggregations at the city or even larger scales. Spatial heterogeneity of crime seasonality, however, often gives rise to opposing seasonal patterns in different kinds of neighborhoods, canceling out seasonality at the city-wide level. Thus past estimates of crime seasonality have vastly underestimated the magnitude and impact of the phenomenon. This paper presents a model for crime seasonality that extends classical decomposition of time series based on a multivariate, cross-sectional, fixed-effects model. The crux of the model is an interaction of monthly seasonal dummy variables with five factor scores representing the urban ecology as viewed from the perspective of major crime theories. The urban ecology factors, interacted with monthly seasonal dummy variables, provide neighborhood-level seasonality estimates. A polynomial in time and fixed effects dummy variables for spatial units control for large temporal and spatial variations in crime data. Our results require crime mapping for implementation by police including thematic mapping of next month's forecasted crime levels (which are dominated by seasonal variations) by grid cell or neighborhood, thematic mapping of the urban ecology for developing an understanding of underlying causes of crime, and ability to zoom into neighborhoods to study recent crime points.(Download)
Policing Crime Guns
Jacqueline Cohen and Jens Ludwig (2003) "Policing Crime Guns - Research in Brief." Working Paper. H.J. Heinz III College, Carnegie Mellon University, Pittsburgh, PA.(Download)
Guns and Youth Violence: An Examination of Crime Guns in One City
Firearms are an important factor in violent crimes. Nationally, the percentage of violent offenses that involve use of a firearm closely tracks changes in the supply of newly manufactured pistols (Figure 1). As more pistols became available their use in violent crimes increased. After 1985, firearms were especially implicated in the dramatic rise in juvenile homicide rates, both as victims (Fingerhut, 1993; Fingerhut, et al., 1998) and offenders (Blumstein, 1995). While juvenile rates of homicides by gun surged upward, both adult and nongun juvenile homicide rates remained relatively flat during the same period (Blumstein and Cork, 1996; Cork, 1996). While the link between guns and youth homicides is compelling in aggregate data, very little is known about how gun availability actually affects individual behavior among youth, whether that effect differs between young adults and juveniles, and whether that relationship has changed over time. The research discussed here examines spatial and temporal features of crime guns in one city. The analysis focuses on attributes of crime guns and those who possess them, the geographic sources of those guns, the distribution of crime guns over neighborhoods in a city, and the relationship between the prevalence of crime guns and incidence of violent crimes especially homicides.(Download)
Impact of Police Raids at Nuisance Bars on Illegal Drug Dealing: Estimating Intervention Effects in Varying Risk Settings
This paper examines the effects of police raids at nuisance bars on drug dealing in and around the nuisance bar. We examine effects of both dosage (number of raids) and duration of the intervention, as well as the conditioning effects of land use and population characteristics in shaping the underlying risk levels of drug dealing in the target and surrounding displacement areas. Results indicate that the police intervention does suppress levels of drug dealing during periods of active enforcement, but these effects largely disappear when the intervention is withdrawn. Also, the effects of the intervention are mediated by risk characteristics in target and displacement areas. In general, target areas characterized by higher levels of risk are more resistant to intervention effects than those with lower levels or risk. Risk factors in nearby displacement areas are also significant. Bars with high levels of risk arising from land uses in surrounding areas are easier to treat, while bars with high levels of population-based risk in surrounding displacement areas are harder to treat.(Download)
Distinguishing Between Effects of Criminality and Drug Use on Violent Offending
The alarming increase in lethal violence among young people in the U.S.-which is often attributed to drug use and drug trafficking-has prompted re-examination of the relationship between drugs and violent offending. While no national data exist, numerous local studies find a high prevalence of homicide deaths among identified drug addicts, a high prevalence of substance use-typically alcohol-among victims of homicide, and a high proportion of persons testing positive for drug use among arrestees for violent offenses. Other studies report large increases in drug-related homicides or other violence associated with drug distribution. In a departure from previous research that contrasts users and nonusers of drugs, or compares broad periods of heavy and light drug use during long addiction careers, the present study attempts to isolate more direct effects of drug use near the time of offending. The data are for a sample of adults arrested in Washington, DC from July 1, 1985 to June 30, 1986, and include their longitudinal arrest histories along with the results of urine drug screens administered following arrest.(Download)