By Dennis Mares and Lindsay Maier 

In 2018 the St. Louis Metropolitan Police Department (SLMPD) was awarded a SPI grant aiming to reduce serious crime by deploying mobile surveillance trailers (MST). The targeted crimes include gun violence and theft of and from vehicles. The SPI award funded three mobile surveillance trailers equipped with license plate readers, cameras and gunshot detection. In addition to the three functioning trailers a fourth shell trailer (placebo) was also purchased to examine if any deterrent impact of the trailers is the outcome of enhanced intelligence capacity or whether the mere presence of the units deter crime by themselves. A total of 95 MST deployments occurred in micro hot spots between June 2020 and July 2022. Data from the SLMPDs CAD and RMS systems were collected continuously to explore the impact of the deployments. Final analysis of the data reveals some crime reductions. Crime reductions were noted in several targeted categories, including gunfire, larcenies and motor vehicle thefts. While crime reductions were found for violent crimes, comparable areas also experienced declines. While the SLMPD’s SPI project faced some challenges throughout its run, the project stayed the course and implementation of the project may be considered successful. There are numerous lessons learned from this project, a couple of the key items are highlighted here, but more can be found throughout this report: 1. Deployment of MSTs should be done by a small group of well-trained individuals. SPI trailers were monitored and received regular maintenance, but setup of the specific investigative components (license plate readers, cameras, and gunshot detection) requires specialized knowledge. We therefore recommend that agencies with a substantial number of trailers consider centralizing the deployment and maintenance of the units to minimize technical issues and reduce downtime. Quality of the MST units can be variable. Technical expertise within the department was a critical resource in expediently resolving wiring issues, for example. We recommend that agencies who purchase such units only do so if they have personnel with the technical expertise to handle and fix problems, or have a clear service contract with a vendor. While the vendor was responsive to problems, the vendor was located far from the region, which would delay service for significant issues. 2. Deployment of MSTs can only be adequately measured if units remain in place for some time and are adequately tracked. In other words: moving the units frequently hampers measurement, whereas leaving them in place too long conceivably reduces deterrent impacts. The SPI MSTs were carefully tracked by the RP, but other MSTs the department owned were tracked on a spreadsheet, which is not only time-consuming, but the information can be outdated quickly. During the course of the project the department improved tracking of all the MSTs . We created two ways to track the units, which could easily replicated in other agencies. We recommend that other agencies find similar ways to track the units, either using GPS trackers or within their CAD system. This allows for easier evaluation of crime prevention strategies but also helps with practical issues such as servicing and refueling trailers. 4. Deployment strategies should not just consider the frequency of crime but also the nature of the location. We found, for example, that the bright flashing blue lights on the trailers caused some annoyance among residents of narrow city streets. In addition, we found that automatic pan-tilt-zoom (PTZ) functions of cameras yielded less actionable footage in narrower streets as the cameras often would end up zoomed in on nearby properties thereby missing movement in the street. In short,  features that are often promoted by vendors may not always be useful in all situations. We therefore recommend discussing with vendors the types of locations in which the technology is typically deployed and customize the units to best fit the needs. 5. The SPI trailers were outfitted not only with cameras and license plate readers, but also with gunshot detection. That latter feature proved superfluous. Not only was the gunshot detection feature fairly inaccurate when compared to existing fixed gunshot technology (i.e., ShotSpotter), results indicate that the presence of the units themselves deters gunfire in close proximity (~500 feet) thereby negating any potential benefits gunshot detection system. In short, gunshot detection capability on visually prominent trailers is likely an inefficient and ineffective feature when deployed in most residential streets. In addition, setting up the gunshot detection can be very time-consuming, which in our case had to be redone every deployment. We therefore do not currently recommend adding gunshot detection to highly visible surveillance trailer as the added cost did not improve investigative benefits. 6. Target specific crime problems for reductions. We advise deploying MSTs in the highest crime locations that are difficult to surveil with traditional fixed systems (CCTV). Our results show that the most likely benefits can be gained from sites experiencing high levels of theft and gunfire, with no conclusive evidence that the units reduce serious violent crimes. 7. Crime reductions appear most commonly in only a small band around the units (~500ft), this makes careful placement important. It is also important to recognize that hot spots often may experience ‘regression to the mean’, meaning that crime often fluctuates in micro hot spots, rapidly heating up and quickly cooling down. This makes evaluating efforts difficult as it is easy to read crime reductions as a result of deployments, while in fact, they are simply returning to baseline levels and might have done so without deployment of MSTs. Using consistent criteria for deployment and measurement as well using comparison locations is therefore key to gain more confidence in results and minimize false conclusions. 8. Support of SLMPD personnel for MSTs became more prominent during the project. Survey results indicate that there was broad support for technology in the department, and especially for technologies that may aid investigations. Awareness of MSTs and their capacities grew substantially as the department expanded its use. 8. Finally and importantly, while it is relatively easy to measure crime at MST sites, it proved extremely difficult to measure how the units enhance intelligence gathering capacity. We encourage agencies to find ways to determine how MSTs and other technologies contribute to solving and prosecuting offenses. With growing public scrutiny of surveillance technology, it is even more important to develop best practices that can most accurately assess the cost-benefits of the technology.

Edwardsville, IL: Southern Illinois University Edwardsville, 2022. 46p.