The Costs and Benefits of a Local DNA Database

Abstract

DNA databases are useful tools for improving public safety. While past research examines the effects of national- or state-level databases, little is known about the distinct benefits of a local, District Attorney-run DNA database. Two key advantages of a local database are that (i) more local criminals submit a sample as part of a plea agreement (submission is not restricted to certain crimes and mandatory) and (ii) response times for identifying reoffenders from DNA evidence are shorter. This report performs a retrospective benefit–cost analysis on the Orange County District Attorney’s DNA database. The analysis is run on administrative records that provide costs, entries into the DNA database, and matches that occur between samples taken from a crime scene and individual profiles in the database. We also estimate the deterrence effect of entry into the database with defendant-case-level data. We find that, for every dollar spent on operating the database over the last 10 years, $1.71 is saved due to the estimated reduction in future offenses.

1. Introduction

DNA databases make it easier for investigators to find and prosecute the perpetrator of a crime. If criminals weigh the expected benefits from a successful crime with the risks of being caught and punished, a collection of their DNA sample also deters future crime by increasing the likelihood of being caught and punished. DNA databases generally mandate sample collection based on the nature of the underlying offense. When DNA collection is part of a plea agreement, however, the sample is voluntarily submitted. Defendant uptake may signal a lower likelihood to reoffend and so improve outcomes upon release while avoiding the public costs of punishment. Prosecutors also have wider discretion on who they offer DNA submission and collect samples that would not otherwise have been submitted to state or federal governments. More, a locally sourced DNA database receives results from crime scene evidence faster than state or federal databases. This study conducts a benefit–cost analysis (BCA) of operating a local DNA database in addition to a state database by comparing operational costs with estimated foregone costs of future crimes. This study not only informs administrators on the merit of a local DNA database, it also examines a mechanism to deter future crimes while avoiding the costs of diversion, probation, and incarceration.

While there has yet to be a BCA of a DNA database, past literature have examined their effect on crime. Briody (2006) compares outcomes between defendants who entered a DNA sample upon conviction and defendants who did not in Queensland, Australia. While the author did not observe differences in reoffense or sentence length, entry correlated with the defendants’ propensity to plead guilty. Doleac (2017), on the other hand, finds a significant deterrence effect of the U.S. Federal DNA database on crime and suggests that DNA databases are more cost-effective than traditional law enforcement. Anker, Doleac, and Landersø (2021) similarly report that an expansion in the cases for which DNA was collected in Denmark decreased recidivism in the following year by up to 42%. These inconsistent results may be due to the correlative methods or small sample size in the first study, which contrasts with the causal estimates and larger samples of the latter two studies. Although smaller in magnitude, our estimate of the deterrence effect coheres with the more rigorous estimates. ¹

Our research extends these studies in a couple of ways. First, both papers employ an instrumental variables approach, which can only estimate the effect of DNA collection for a subset of the population of interest. The matching estimator we employ here is only limited by the availability of a suitable match in the control group. Our individual-level analysis is also considerably more robust, due to a much larger sample size than that of both Doleac (2017) and Anker et al. (2021), while also containing observed DNA database entry information that was not obtained in Doleac (2017). Recall, too, that the aforementioned features of the local DNA database studied here are distinct from the databases examined in past research.

The first DNA database in the United States was implemented in Colorado in 1988. This tool expanded nationwide soon after with the DNA Identification Act of 1994, which funded federal DNA laboratories and authorized the compiling of a DNA database. The federal government also assisted in the creation of state-level DNA databases. By 1999, every state had complied with the National DNA Index System and created a database within the Combined DNA Index System (CODIS) structure. California began collecting DNA in 1994. Voters in the state expanded the cases in which DNA was collected and used by passing Proposition 69, “DNA Fingerprint, Unsolved Crime, and Innocence Protection Act,” in November, 2004. These databases differ in the crimes for which a defendant must provide a DNA sample. Individuals charged with federal offenses, including terrorism, violent crimes, or sexual offenses, have DNA collected by the federal government, though this sample is removed if the suspect is not charged or convicted, or their conviction is overturned. In California, someone arrested on suspicion of a felony or convicted of a felony has their sample entered into the state database (i.e., CODIS) where it may remain indefinitely.

The Orange County, California Board of Supervisors, approved the allocation of local funds to create the Orange County (OC) DNA database in 2007. ² Entry into this DNA database is voluntary. Defendants who face misdemeanor charges either enter the database voluntarily in lieu of a conviction or as part of a plea agreement. Samples are submitted to a private company, an accredited DNA laboratory, for testing. Advantages of this local database are the wider span of crimes for which collection occurs and a quicker turn-around time for prosecutors to receive results, particularly when using a Rapid DNA instrument. The Orange County District Attorney’s Office (OCDA) can run a DNA analysis on a sample and compare it to their DNA database with results in less than 2 hours, whereas state and federal databases can take weeks, if not months. ³ Roth (2019) studied the OC DNA database through field interviews and public records. Two of her main criticisms, tested here, are that (i) there are diminishing returns to the database wherein the costs exceed the benefits and that (ii) public safety is compromised due to a backlog of samples in need of testing, which delay convictions.

Our main question is whether the benefits of a local DNA database outweigh the costs. Since state and federal databases are already a resource for local district attorney offices, the results from past studies may not apply in the present case. More importantly, there may be no unique deterrence effect from local DNA collection. On the other hand, if such a database is cost effective, it may be a viable option for prosecutors to divert cases, reach plea agreements that reduce punishments, deter future offenses, and resolve future offenses more quickly. We estimate benefits and costs with case-defendant data published by the OCDA coupled with office-provided records of entrants into the DNA database and reasons for entry. After summarizing these data in the following section, we describe our methods for estimating the benefits and costs. Results are then presented. Over the last 10 years, we find that an additional dollar spent on the operational expenses of the DNA database results in a $1.71 reduction in the estimated cost of crime. We conclude by discussing the implications of the results, limits to our study, and suggestions for future research.

2. Data and methods

A retrospective BCA will be conducted from 2006 to 2022 that allows the costs and benefits to vary over time. Costs are provided by the OCDA and described below. Benefits are estimated as foregone costs – namely, reduced reoffenses due to solving or deterring crime – and so our methods exclude the intangible benefits of reduced crimes, victim’s knowledge about a criminal is apprehended and punished, and enhanced public safety. These limitations are a common problem with estimating the benefits of criminal justice policy and practice, and so not unique to this study. Despite these limits, the estimated benefits are likely a lower bound since the administrative costs are well-defined. That is, except for the costs of starting and running the local database, there are no costs associated with the prosecutors use of DNA collection in lieu of dismissal or as part of a plea agreement, nor obvious non-monetized costs to the community. After describing the costs, we summarize the calculation used to estimate benefits.

According to office records, the local DNA database had net aggregate costs of nearly $40 million and has a current annual operating budget of $3 million. Administrative records of costs include salaries, employee benefits, supplies, and services expenditures for fiscal years 2006–2022. ⁴ Costs figures are adjusted for inflation and presented in 2022 dollars. ⁵ To account for the fixed costs of the office, we reduced supply and service costs by 10% and labor costs by 50%. ⁶

Figure 1 shows how total costs of the OC DNA program evolved. Before the program began (fiscal year 2006), there were no supply expenses and expenditures were approximately $800,000. Supplies and personal spending increase through 2010 with total yearly spending plateauing around $2 million. In 2014, net spending increased again until attaining the peak cost of the program in 2017 at $3.4 million. Costs decreased slightly after 2018 till reaching roughly $2.75 million in fiscal year 2022. The net aggregate costs of operating the DNA program during the entire period totaled $39,838,208.10. Revenues obtained by DNA processing fees, DNA collections, and Proposition 69 funds offset some of these costs as well. ⁷ This revenue totals $14,447,009. Below, costs are reduced by annual revenues.

Figure 1. Costs by year. Note: Figure shows the costs for salaries, supplies, and both added together (total) by fiscal year. Salary data is offset by revenues generated in each year. The beginning of the fiscal year is on the x-axis. Data come from the OC District Attorney’s Office.

The efficiency of the DNA database depends less on net costs than on cost per match between a DNA sample taken at a crime scene and an individual DNA profile in the database – a “hit” or investigative lead. Hits are credited to OC DNA for one of the four reasons: (1) the OC DNA hit was unique or did not also hit in CODIS within 10 days of the OC DNA hit; (2) the DNA hit in CODIS but was in the database because of a specimen that was collected by the OCDA as a result of PC 296(a)(5) ⁸; (3) the hit results from OCDA’s Rapid program; and (4) the hit was from outside the county but credited to OC DNA by the California Department of Justice since the sample was collected by OCDA per PC 296(a)(5).

The number of hits has changed over time. Figure 2 shows annual hits from 2010 to 2023 by the four types of OC DNA hits defined above. ⁹ The earlier years (2007–2009) are excluded since searches were not conducted as the database held few samples. In the last 13 years, the OC DNA database grew significantly, which led to more hits. On average, the OC DNA program produced 211 hits per year since 2015. Among them, 87 are PC 296(a)(5) collections, 30 are Rapid hits, 70 were not identified in CODIS, and 24 came from out of county. The highest number of hits occurred in 2019 (255).

Figure 2. OCDNA hits per year. Note: Figure provides annual counts of the number of hits attributable to the OCDNA program for the four types of hits: (1) the OC DNA hit was unique and did not also hit in CODIS within 10 days of the OC DNA hit; (2) the DNA hit in CODIS but was in the database because of a specimen collected by the OCDA as a result of PC 296(a)(5); (3) the hit results from OCDA’s Rapid program; (4) the hit was from outside the county but credited to OC DNA by the California Department of Justice since the sample was collected by OCDA per PC 296(a)(5). Data come from the OC District Attorney’s Office.

Given the number of hits per year, we now calculate the net costs per hit. While program costs have increased (see Figure 1), so as the number of hits (Figure 2). Figure 3 shows the cost for one hit by dividing the total net spending for each year by the number of hits that year. For example, there were 77 hits in 2010 with a net spending of $2.47 million. As a result, the cost per hit was $32,102. Since the slope of hits was higher than the slope of costs, the spending per hit dropped 67% from 2010 to 2016 ($10,667 per hit in 2016). Between 2017 and 2022, the average per-hit cost was $13,815.

Figure 3. Net costs per hit. Note: Figure shows the net spending per hit in each fiscal year. The beginning of the fiscal year is on the x-axis. Spending per hit is on the y-axis, is adjusted for inflation, and expressed in 2022 dollars. Spending includes salaries and supplies. Data come from the OC District Attorney’s Office.

The administrative data provided by OCDA as well as their data on prosecution have important limitations. Cases involving a DNA hit and the resulting case disposition are observed; however, the data cannot show the potential resolution if not for the local DNA database. This limit obscures which types of cases more often lead to a hit and their case length. These factors are benefits, not costs, and so the results of this analysis are a lower bound.

Having described how costs are calculated, we turn to benefits. The impact of the OC DNA program is quantified by the reduction in reoffenses by crime type and by the cost savings associated with the reduction in reoffenses. The estimates produced in this report use the RAND Cost of Crime Calculator and cost of crime estimates from Miller, Cohen, Swedler, Ali, and Hendrie (2021) as a supplement for crime categories not covered in the RAND Cost of Crime Calculator. These studies estimate the cost of crime via both direct costs of victimization (e.g., costs of health care, property damages) and criminality (e.g., the judicial process and incarceration), as well as more indirect costs such as losses in productivity and quality of life. While the literature relied on to estimate forgone costs attempts to account for some intangible costs (e.g., lost productivity of victims), some of the most important benefits of solving a crime are excluded: that is, the psychological benefits to the victim and impacted community and an increase in public safety.

The reduction in reoffenses is estimated in two steps. First, the total reduction in future offenses in OC is estimated by crediting each hit with a 13.64% reduction in reoffenses. For the estimate of this deterrence effect, see Appendix A. The 2,428 hits credited to OCDNA results in 331.18 fewer future reoffenses. Next, the types of crimes avoided are assumed to follow the distribution of the “top” charges ¹⁰ filed in OC since 2013. ^{11 , 12}

An illustrative example of the reduction in future offenses is found by examining burglaries. From the 2,428 hits credited to the OCDNA program, 331.18 future offenses will be avoided, since these hits may have never occurred if the criminal justice system in OC solely relied on the CODIS database. Of felony “top” charges ¹³ filed in OC since 2013, 11.09% (15,042/135,662) were burglaries. This implies a reduction of 36.7 burglaries. This process is repeated across all crime types. Table 1 provides the estimated reduction in recidivism that resulted from hits in the OCDNA database by crime type. The largest reductions in reoffenses are attributable to drug offenses (82), burglary (37), aggravated assault (35), and motor vehicle theft (34). ¹⁴

Table 1. Summary of deterrence and savings calculations by crime

Note: Calculations for how hits from the OCDNA database affect deterrence by crime type. Column 2 shows reductions in reoffenses. Column 3 displays which study the cost estimates are derived from. Column 4 displays cost of crime estimates in 2022 dollars to facilitate comparisons to the cost data. Column 5 shows estimated savings from reduced crime. See Table A1 in Appendix A for mapping of Orange County crime categories to the crime categories in Heaton (2010) and Miller et al. (2021).

The second measure used for calculating the effect of the OCDNA database on community safety is the cost savings that resulted from fewer re-offenses. Using the RAND Cost of Crime Calculator (Heaton, 2010) and Miller et al. (2021) as a supplement for crimes not included in Heaton (2010), a cost is associated with each crime type and displayed in column 4 of Table 1. Column 2 shows the deterred crimes, column 3 the study used for the estimated cost per crime of a given type, then the cost estimate, and the fifth column shows the savings resulting for the crimes deterred and cost per crime. Overall, the OC DNA database yields an aggregate cost reduction of $52,670,244.

3. Results

Given the evolving costs and benefits, results are shown over time. The dynamic element comes from comparing the yearly net cost per hit with the deterred crimes. Despite the number of entrants and even decreasing operational costs, fewer hits raise the net cost of the database. More hits reduce costs. One concern, then, is whether the database results in enough hits to regularly clear costs; however, the deterred crimes from entry into the database also lessen costs. We find that benefits clear costs in 2012, exactly 5 years after the OCDA received approval to begin the DNA database. The benefits remain strongly positive thereafter.

Figure 4a shows the monetary benefits associated with less recidivism minus the net costs (total supplies and salary minus revenue). To calculate the annual monetary benefits, the number of hits (Figure 2) is used to weight the estimated savings from Table 1 to different years. For example, there were 77/2,319 (3.32%) hits in 2010. ¹⁵ The subsequent benefits due to deterred reoffenses are $1,748,861 in 2010, which are then subtracted by the net costs of $2.47 million. Thus, the OC DNA program produced $722,979 in net losses in 2010.

Figure 4. Comparison of benefits to costs. Note: Figures show the yearly net costs of OC DNA compared to the yearly benefits of OC DNA. In all figures, the estimated benefits are allocated across years by the fraction of the total hits produced that occurred in that year. See Sections 3 and 4 for details on how the benefits are calculated and Table 1 for a summary of the benefit estimates. For costs, salaries of all employee types and the costs of supplies are included. For (a), the line shows the benefits (in terms of reduced future crime) minus the net costs (in terms of supplies and salaries less revenues) for each year. For (b), the line shows the benefits divided by the net costs for each year. Data come from the OC District Attorney’s Office.

The Return on Investment (ROI) turns positive after 2012. By 2016, the benefits exceed the costs by $2,926,959. There is a dip in benefits in 2017, when spending peaked (see Figure 1), yet the program yielded net benefits of $1,468,433. Since 2018, benefits exceeded costs by $2,301,193, on average.

The aforementioned results are reported as a ratio of benefits to net costs in Figure 4b. When the program was first credited with hits in 2010, the benefits in terms of reduced crime were 71% of the costs: that is, an additional dollar spent on the OC DNA program in 2010 would has reduced future crime costs by 71 cents. The ratio rises to 1.52 in 2022 and averages 1.51 over the entire period. Since 2013, benefits have cleared or exceeded net costs. Considering only 2013 to 2022, the benefit–cost ratio averaged 1.71, which means that each dollar spent on the DNA program yields $1.71 in benefits.

To test the robustness of the above results, we perform the following sensitivity analysis: we alter the estimates from Miller et al. (2021) and Heaton (2010) of the cost of crime by 10% and 20% and see how the estimated benefit–cost ratio fluctuates. Given the acknowledged limits with these estimates of the cost of crime, these adjustments show a plausible bound around what we argued above is a conservative estimate. Figure 5 presents these results. The positive ratio persists after the third year of the OC DNA program despite reductions of $5.27 million (10%) and $10.53 million (20%).

Figure 5. Comparison of benefits to costs. Note: Figures show the yearly net costs of OCDNA compared to the yearly benefits of OCDNA for 10% and 20% reductions and increases in the estimated costs of crime. In both figures, the estimated benefits are allocated across years by the fraction of the total hits produced that occurred in that year. See Section 2 for details on how the benefits are calculated and Table 1 for a summary of the benefit estimates. For costs, salaries of all employee types and the costs of supplies are included. For (a), the line shows the benefits (in terms of reduced future crime) minus the net costs (in terms of supplies and salaries less revenues) for each year. For (b), the line shows the benefits divided by the net costs for each year. Data come from the OC District Attorney’s Office.

4. Discussion

The total savings attributed to the OC DNA program is about $52.7 million over the life of the program. These cost reductions from reoffenses likely increase in recent years as the database produces more hits. Relative to the lifetime costs of operating the program, the average benefit–cost ratio is roughly 1.51. This is well higher than the common threshold of determining the financial feasibility of a project, which is 1. As mentioned in Section 2, moreover, this ratio is a conservative estimate given other intangible benefits that are excluded. In this final section, we consider the consequences of these findings, their limitations, and recommendations for future research.

Results suggest that counties relevantly similar to OC would benefit from operating a local DNA database in addition to a state database as a cost-effective strategy for resolving and deterring crime. Various factors may influence such a database’s success or failure. Entry into the OC DNA database is voluntary and is often negotiated as part of a plea agreement. Defendants who elect to enter the database may relevantly differ from defendants who refuse or those for whom entry is not offered. The impact of a local database may differ depending on the conditions for entry. These conditions may also influence the deterrence effect of entry. Since benefits are defined here as the foregone costs of reoffenses, differences in the likelihood of defendants who enter to reoffend may dramatically influence the cost–benefit calculation.

This study has limits with how benefits and costs are calculated. If these limits are addressed, the results may change. The costs of operating the OC DNA program exclude the legal or political costs: a database may make a DA Office more susceptible to lawsuit or lessen the electability of a DA. But there are potential benefits along the same lines that are excluded. DA Offices may benefit from increased access to DNA evidence when prosecuting crimes besides the quicker resolution of cases. For example, certain charges may be pursued that otherwise would have lacked sufficient evidence. When running for office, a DA may benefit politically from forming a DNA database. We also exclude the psychological benefits to victims of solving crimes and the similar benefits to a community when public safety improves.

There are a few directions for future research. Cost estimates gain precision if researchers worked with an in-house budget analyst to specify prosecution, law enforcement, and court costs. These costs could then be used to estimate the average cost of a case per day, which would contribute to an analysis of the benefits of resolving cases more quickly. If cases that resulted in entry into the DNA database were linked with data on which later cases resulted in a hit, researchers could also examine how plea agreements and sentences impact future criminal behavior. Better estimates of the DNA database’s deterrence effect could also be obtained from causal estimates, which specify the effect of the database by addressing selection bias.

DA Offices form part of the critical criminal justice infrastructure to ensure public safety by maintaining rule of law. Our results cohere with findings from other research that DNA databases are useful tools in reducing criminal behavior. The OC DNA database has produced a total of 6,911 hits over 14 years of the program’s existence, 2,428 of which were unique and credited exclusively to the OC DNA database. Although we are unable to determine the causal relationship between hits and arrests, charges filed, or convictions, we calculated best estimates for the value add of the database and compared these benefits to operational costs. Over the last 10 years, a dollar spent on operating the DNA database has yielded $1.71 in reduced costs from criminal reoffenses. This result justifies the continued use of the database and promotes its adoption in other jurisdictions.