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Washington State Institute for Public Policy
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Police diversion for individuals with mental illness (pre-arrest)

Adult Criminal Justice
Benefit-cost methods last updated December 2024.  Literature review updated March 2017.
Diversion programs for individuals with mental illness redirect these individuals from the traditional criminal justice system into mental health treatment programs.
This review focuses on pre-arrest diversion programs, which are police-based programs. Police-based diversion programs divert participants to services without applying criminal charges. Programs included in this meta-analysis followed the Crisis Intervention Team model, which involves specialized police training and partnerships between police and mental health providers in the community. Mental health courts and post-arrest diversion programs were reviewed separately from this meta-analysis.
 
ALL
BENEFIT-COST
META-ANALYSIS
CITATIONS
For an overview of WSIPP's Benefit-Cost Model, please see this guide. The estimates shown are present value, life cycle benefits and costs. All dollars are expressed in the base year chosen for this analysis (2023).  The chance the benefits exceed the costs are derived from a Monte Carlo risk analysis. The details on this, as well as the economic discount rates and other relevant parameters are described in our Technical Documentation.
Benefit-Cost Summary Statistics Per Participant
Benefits to:
Taxpayers ($1,553) Benefits minus costs ($19,351)
Participants ($635) Benefit to cost ratio ($2.31)
Others ($1,841) Chance the program will produce
Indirect ($9,475) benefits greater than the costs 24%
Total benefits ($13,503)
Net program cost ($5,848)
Benefits minus cost ($19,351)

^WSIPP’s benefit-cost model does not monetize this outcome.

Meta-analysis is a statistical method to combine the results from separate studies on a program, policy, or topic to estimate its effect on an outcome. WSIPP systematically evaluates all credible evaluations we can locate on each topic. The outcomes measured are the program impacts measured in the research literature (for example, impacts on crime or educational attainment). Treatment N represents the total number of individuals or units in the treatment group across the included studies.

An effect size (ES) is a standard metric that summarizes the degree to which a program or policy affects a measured outcome. If the effect size is positive, the outcome increases. If the effect size is negative, the outcome decreases. See Estimating Program Effects Using Effect Sizes for additional information on how we estimate effect sizes.

The effect size may be adjusted from the unadjusted effect size estimated in the meta-analysis. Historically, WSIPP adjusted effect sizes to some programs based on the methodological characteristics of the study. For programs reviewed in 2024 or later, we do not make additional adjustments, and we use the unadjusted effect size whenever we run a benefit-cost analysis.

Research shows the magnitude of effects may change over time. For those effect sizes, we estimate outcome-based adjustments, which we apply between the first time ES is estimated and the second time ES is estimated. More details about these adjustments can be found in our Technical Documentation.

Meta-Analysis of Program Effects
Outcomes measured Treatment age No. of effect sizes Treatment N Effect sizes (ES) and standard errors (SE) used in the benefit-cost analysis Unadjusted effect size (random effects model)
First time ES is estimated Second time ES is estimated
ES SE Age ES SE Age ES p-value
Crime
Any criminal conviction according to court records, sometimes measured through charges, arrests, incarceration, or self-report.
 37 3 290 0.089 0.081 38 0.089 0.081 46 0.089 0.275
Alcohol use disorder
Clinical diagnosis of alcohol use disorder or symptoms measured on a validated scale.  
 37 3 290 0.068 0.170 37 0.000 0.187 40 0.068 0.690
Illicit drug use disorder
Clinical diagnosis of illicit drug use disorder or symptoms measured on a validated scale. When possible, we exclude cannabis/marijuana use disorder from this outcome.
 37 3 290 0.325 0.205 37 0.000 0.187 40 0.325 0.113
Psychiatric symptoms^
Mental health symptoms (such as symptoms of psychosis) in individuals with serious mental illness, measured on a validated scale.
 37 3 290 0.036 0.081 37 n/a n/a n/a 0.036 0.659
Emergency department visits
Whether someone visited the emergency department, or the number of times they visited the emergency department.
37 3 290 0.289 0.388 37 0.000 0.118 38 0.289 0.456
Homelessness^
A lack of stable housing, often measured through self-report of conditions like living on streets or in shelters in a given time period.
 37 3 290 0.059 0.186 37 n/a n/a n/a 0.059 0.751
1In addition to the outcomes measured in the meta-analysis table, WSIPP measures benefits and costs estimated from other outcomes associated with those reported in the evaluation literature. For example, empirical research demonstrates that high school graduation leads to reduced crime. These associated measures provide a more complete picture of the detailed costs and benefits of the program.

2“Others” includes benefits to people other than taxpayers and participants. Depending on the program, it could include reductions in crime victimization, the economic benefits from a more educated workforce, and the benefits from employer-paid health insurance.

3“Indirect benefits” includes estimates of the net changes in the value of a statistical life and net changes in the deadweight costs of taxation.
Detailed Monetary Benefit Estimates Per Participant
Affected outcome: Resulting benefits:1 Benefits accrue to:
Taxpayers Participants Others2 Indirect3 Total
Crime Criminal justice system ($601) $0 ($1,095) ($301) ($1,997)
Alcohol use disorder Property loss associated with alcohol abuse or dependence $0 ($1) ($2) $0 ($2)
Illicit drug use disorder Labor market earnings associated with illicit drug abuse or dependence ($165) ($389) $0 $0 ($555)
Health care associated with illicit drug abuse or dependence ($729) ($110) ($744) ($364) ($1,948)
Mortality associated with illicit drugs ($57) ($135) $0 ($5,886) ($6,078)
Program cost Adjustment for deadweight cost of program $0 $0 $0 ($2,924) ($2,924)
Totals ($1,553) ($635) ($1,841) ($9,475) ($13,503)
Click here to see populations selected
Detailed Annual Cost Estimates Per Participant
Annual cost Year dollars Summary
Program costs $8,347 2016 Present value of net program costs (in 2023 dollars) ($5,848)
Comparison costs $3,537 2015 Cost range (+ or -) 10%
Program costs include general program administration/coordination costs from Cowell et al., 2015 combined with the difference in treatment costs between experimental and control groups in Cowell et al., 2004. Control group costs are from WSIPP’s internal estimates of the cost of 77 days of jail. Cowell, A. J., Hinde, J. M., Broner, N., & Aldridge, A. P. (2015). The cost of implementing a jail diversion program for people with mental illness in San Antonio, Texas. Evaluation and Program Planning, 48, 57–62. Cowell, A.J., Broner, N., & Dupont, R. (2004). The Cost-effectiveness of criminal justice diversion programs for people with serious mental illness co-occurring with substance abuse four case studies. Journal of Contemporary Criminal Justice, 20(3), 292-314.
The figures shown are estimates of the costs to implement programs in Washington. The comparison group costs reflect either no treatment or treatment as usual, depending on how effect sizes were calculated in the meta-analysis. The cost range reported above reflects potential variation or uncertainty in the cost estimate; more detail can be found in our Technical Documentation.
Benefits Minus Costs
Benefits by Perspective
Taxpayer Benefits by Source of Value
Benefits Minus Costs Over Time (Cumulative Discounted Dollars)
The graph above illustrates the estimated cumulative net benefits per-participant for the first fifty years beyond the initial investment in the program. We present these cash flows in discounted dollars. If the dollars are negative (bars below $0 line), the cumulative benefits do not outweigh the cost of the program up to that point in time. The program breaks even when the dollars reach $0. At this point, the total benefits to participants, taxpayers, and others, are equal to the cost of the program. If the dollars are above $0, the benefits of the program exceed the initial investment.

Citations Used in the Meta-Analysis

Broner, N., Lattimore, P.K., Cowell, A.J., & Schlenger, W.E. (2004). Effects of diversion on adults with co-occurring mental illness and substance use: Outcomes from a national multi-site study. Behavior Sciences and the Law, 22(4), 519-541.