OnPolicing Blog

A recent article on stops and searches by the Metropolitan Police in London has reignited debate about the use of stop, question, and frisk (SQF) in the United States. Piquero and Sherman (2025)¹ analyzed 15 years of stop and search data from the Metropolitan Police and found a correlation between increases and decreases in stop and search encounters (SSE) and subsequent rates of serious injuries and homicides in London, primarily from knife attacks. In short, knife-related assaults and deaths went down when British police stopped and searched more people in public, and they went up when police stopped and searched fewer people. What do these findings mean for U.S. law enforcement? Should police in America stop and frisk more people as a strategy to reduce violent street crime, crimes that in the U.S. usually involve guns rather than knives?

The English Version of SQF

England doesn’t have a Fourth Amendment, and police in London (and elsewhere in England) can stop and question anyone at any time and search them based on “reasonable grounds” that they may be carrying illegal drugs, a weapon, stolen property, or anything else that could be used to commit a long list of specified crimes.² Thus, the legal authority of the Metropolitan Police to stop and search individuals is much broader than in the U.S. From 2008-2011, the number of SSEs conducted by the Metropolitan police averaged about 45,000 per month, which seems like a lot of SSEs. By way of comparison, New York City was about the same size as London during those years, and the NYPD reported conducting even more SQFs per month (around 57,000) in 2011 at the height of its use of SQF as a crime control strategy.

SQF in the U.S.

Every police officer in America is familiar with Terry v. Ohio, where in 1968, the United States Supreme Court permitted the brief detention and frisk of a suspect based on a “reasonable suspicion” that he was about to commit an armed robbery. Terry established that police could briefly detain people based on less than probable cause and frisk their outer clothing if they had reason to believe those individuals were armed and dangerous. While Terry involved a crime that was imminent but had not yet been committed, subsequent cases have extended its rationale to recently committed crimes as well. Today, police officers in the U.S. can lawfully detain persons under the Fourth Amendment based on reasonable suspicion (a low evidentiary standard) that they are about to or have just committed a crime, and they can frisk them for weapons if they have further reason to believe they may be armed and dangerous. Importantly, reasonable suspicion must be individualized under U.S. Supreme Court rulings. Officers cannot apply suspicion to entire groups or categories of people, although the level of crime in the area where a stop takes place, along with other individual factors, can be considered in determining reasonable suspicion.

SQF as a Crime Reduction Strategy

Beginning in the late 1990s and continuing for the next 10 years, the NYPD at times used SQF as a strategy to reduce gun violence or implicitly encouraged its use as part of a Compstat performance management system that evaluated supervisors on metrics associated with SQF. As a result, the number of SQFs in New York skyrocketed between 1993 and 2011. In 2008, the Center for Constitutional Rights filed a class action suit in federal district court³ and challenged the NYPD’s use of SQF on constitutional grounds. Following a bench trial, the NYPD became the only police department in the country to ever be found liable for a pattern and practice of unconstitutional policing related to how the agency implemented its SQF practices.

Long before the recent study of SSEs in London, much had been written about the effectiveness of SQF in reducing street crime, and a number of studies both in the U.S. and internationally have demonstrated its effectiveness at reducing crime when intensively applied. A recent meta-analysis of 40 SQF studies found a statistically significant 13% reduction in crime within SQF treated areas compared to controls. That same study, however, also documented a range of harmful individual-level effects of SQF, including negative impacts on mental and physical health, perceptions of the police, and self-reported levels of crime and delinquency.

At the community level, intensive use of SQF is thought to reduce community trust in the police and increase perceptions of racial bias. Indeed, the federal court in the NYPD SQF case found that police not only had engaged in an unconstitutional pattern of targeting minority individuals and neighborhoods for stops and frisks but that this contributed to community distrust and discontent with the NYPD. The court also found that many of the stops examined lacked individualized reasonable suspicion.

The Important Role of SQF in Policing

We fully support the use of SQF by the police for investigative and individual crime prevention purposes. In Terry v. Ohio, Officer McFadden relied upon his 40 years of experience as a Cleveland police officer to interrupt and prevent the armed robbery of jewelry store. Similarly, officers make thousands of well-supported stops of crime suspects every day, resulting in crimes being solved, illegal contraband recoveries, and enhanced community safety. The Supreme Court has long approved of such stops, and they are an important public safety tool when used appropriately. But the use of SQF as a blunt and persistent instrument to reduce violence in high crime areas carries more risks than benefits, especially when better, evidence-based alternatives are available.

Alternatives to SQF for Crime Reduction

Research has repeatedly demonstrated that violent crime is highly concentrated geographically and by person. Recent data from Dallas and San Antonio, for example show that less than 2% of the land area in those cities accounted for 50% of all reported violent street crime (murder, robbery, aggravated assault). Likewise, more than 90% of the land area in those two large cities produced no violent street crime. At the person level, a 2017 meta-analysis of more than 30 studies of criminal offending found that 10% of the most criminally active persons accounted for 66% of reported crime.[4] Finally, research demonstrates that crime is concentrated temporally as well as spatially. Certain hours of the day and days of the week are much more likely to see violent crime than others, and those temporal crime patterns vary considerably from place to place.

Hot Spots Policing

Armed with this knowledge, law enforcement agencies can effectively utilize evidence-based strategies to help reduce violent crime more efficiently and without alienating the communities they serve and whose trust they need to solve crimes and maintain public safety. One strategy that research has repeatedly shown to be effective is hot spots policing. But not all hot spots policing strategies are equally effective.

A 21st-century hot spots policing approach deploys officers to a relatively small number of hot spots for 60-90 days at a time based on careful analysis of the spatial and temporal distribution of crime in the previous 60-90 days. The best predictor of where crime is likely to occur this month is where it occurred last month. The goal is for officers to be highly visible (all emergency lights activated) at hot spots during peak crime hours, which again, vary from hot spot to hot spot. While their patrol cars are illuminated and parked for only 15 minutes during peak crime hours, officers should get out, walk around, talk to residents and business owners, and listen to what the community is telling them.

Whenever possible, these contacts should be pro-social rather than heavy-handed. Stops and frisks may be necessary if and when circumstances warrant, but stop and frisk is not the goal. Modern hot spots strategies (1) are precise and focused on the relatively few, small areas (100m x 100m grids), addresses, or street segments that recorded most of the violent crime in the past 60 days, (2) designed with sufficient dosage (police presence) to serve as a deterrent to would-be offenders, and (3) utilize light footprint tactics to produce a sense of safety and guardianship without leaving residents who live in and around hot spots feeling threatened.

Problem-Oriented, Place-Based Policing

Hot spots policing is an effective “fever reducer.” When executed with precision and fidelity, it can help lower the “crime temperature” at hot spots, but it is not going to reduce violent crime at persistently violent places by itself over the long-term. Repeat hot spots need an additional problem-driven strategy to identify and remediate the underlying conditions that make such places conducive to crime. Persistently violent places often have environmental and social features that make them attractive locations for violence. These places need a multi-disciplinary approach that brings city government (not just the police) and local stakeholders (e.g., apartment complex owners and managers) together to address the underlying conditions that make them criminogenic. Crime prevention through environmental design (CPTED) changes, afterschool activities for youth, building repairs, and other physical improvements are often needed. At the same time, high levels of crime, often caused by a relatively few individuals or groups, must be addressed by law enforcement stakeholders to help set the conditions for success. Environmental and social improvements cannot successfully take root if people are afraid and high levels of violence are allowed to persist. Police must work hand-in-hand with other city stakeholders and the community to help set the conditions for longer term success.

This work is not easy and requires leadership at the local government level (mayor’s or city manager’s office) to bring different city agencies together in a workgroup whose function is to identify the underlying problems driving high levels of crime at a hot spot, design strategies to address those problems, and then hold everyone accountable for doing their part. Since these kinds of persistently violent places produce an outsized share of the total violent crime reported in a jurisdiction, reducing crime at just a few of them can have a demonstrable effect on overall levels of reported violent crime, though.

Focused Deterrence

Focused deterrence is an evidence-based strategy that addresses criminogenic people rather than places. It uses data to identify the high-risk violent offenders who account for much of the violent crime in a jurisdiction and then targets them with a “carrot and stick” approach. They are offered a choice between continued criminal involvement that will lead to enhanced prosecution for them and their associates, or a set of tailored social services designed to help them desist from violence and make better life choices. Life plans are individualized for each offender and may involve housing, job training, substance abuse treatment, and even cognitive behavioral therapy. When possible under state and local rules, offenders on probation and parole are mandated to attend “call-in” sessions where they hear from law enforcement officials, victims of violence, and service providers, and are offered the opportunity to participate in the program. The alternative is targeted enforcement for continued violence, enhanced prosecution using federal partners if possible, and lengthy prison sentences for those convicted.

There are many different focused deterrence models that have been implemented and evaluated in cities across the U.S. over the last 30 years. While these programs can be complex and resource-intensive, focused deterrence is one of the few person-based violence reduction strategies that has shown success in helping to divert high-risk offenders from continuing their violent lifestyles.

Conclusion

Individually, these three strategies – hot spots policing, problem-oriented, place-based policing, and focused deterrence – have proven track records of success. When layered together in a comprehensive strategic plan, they can work synergistically to reduce violent crime across an entire major city as recent evidence has demonstrated in Dallas and San Antonio. When implemented appropriately, they can be far more impactful and less potentially harmful to communities than flooding high crime neighborhoods with police and encouraging the widespread use of stop and frisk.

References

¹ Piquero, A.R. & Sherman, L.W. (2025). Did more stop and search by police cause less knife injury in London? Evidence from 2008-2023. Journal of Quantitative Criminology. https://doi.org/10.1007/s10940-025-09609-7.

² See U.K. Government. Police powers to stop and search: your rights (https://www.gov.uk/police-powers-to-stop-and-search-your-rights/police-powers-stop-search); Public Order Act 2023. UK Public General Acts, c. 15 Part 1 (Eng).

³ Floyd v. City of N.Y., 959 F. Supp. 2d. 540 (S.D.N.Y. 2013).

⁴ Martinez, N.N., Lee, Y., Eck, J.E., & O, S. (2017). Ravenous wolves revisited: A systematic review of offending concentration. Crime Science, 6(10). DOI 10.1186/s40163-017-0072-2.