GOP presidential nominee Donald Trump came out in favor of stop-and-frisk at an event in an Ohio church on Wednesday.

According to The New York Times, Trump was asked how he would lower crime in the black community.

"One of the things I’d do, is I would do stop-and-frisk," Trump responded. "I think you have to. We did it in New York, it worked incredibly well and you have to be proactive."

Naturally the Times goes on to quote a variety of leftists condemning Trump's support of stop-and-frisk as a trigger "alienating" the black community.

Here are five things you need to know about stop-and-frisk.

1. What is stop-and-frisk? According to Cornell University Law School, stop-and-frisk involves the police stopping people when there is "a reasonable suspicion that a crime has been, is being, or is about to be committed" and then patting them down to see if they have a weapon on them.

2. Stop-and-frisk is one of the reason's for New York City's sharp decline in crime. According to Heather Mac Donald, murders declined almost 80 percent and major felonies by almost 75 percent from the early 1990's to 2013 thanks to "proactive policing," which includes the practice of stop-and-frisk.

In 2011, "stops yielded nearly 800 guns and over 5,000 other weapons, mostly knives," according to Mac Donald. Critics of the practice argue that this isn't enough to justify its use, and they also claim there aren't enough arrests from the practice to justify it. However, Mac Donald points out that "the possibility of getting stopped has clearly deterred many gangbangers from packing heat — which is precisely the point" as well as deterred other crimes from being committed.

3. Stop-and-frisk is not racist. This is the common refrain from stop-and-frisk critics, and Mac Donald proves how ludicrous it is using 2011 data:

Blacks are 53 percent of stop subjects, though they are 23 percent of the city’s population. Whites are 9 percent of stop subjects, though they are 35 percent of the city’s population. Therefore, conclude Stringer and others, the NYPD targets individuals for stops based on their race rather than on crime patterns and suspicious behavior.

Here is what the anti-cop critics never divulge: Blacks are 66 percent of all violent-crime suspects, according to the victims of and witnesses to those crimes. Blacks commit around 70 percent of all robberies and about 80 percent of all shootings in the city. Add Hispanic shooters, and you account for 98 percent of all shootings in the city.

Whites, by contrast, were only 5 percent of all violent crime suspects in 2011. According to victim and witness reports, they commit barely over 1 percent of all shootings and less than 5 percent of all robberies.

Such disparities mean that the police can’t deploy their resources where people most need protection from violence — in minority neighborhoods — without producing racially disproportionate stops.

The numbers are similar from 2012 as well:

The claim ignores the reality that the preponderance of crime perpetrators, and victims, in New York are also minorities. Blacks, for example, constituted 78% of shooting suspects and 74% of all shooting victims in 2012, even though they are less than 23% of the city's population.

Whites, by contrast, committed just over 2% of shootings and were under 3% of shooting victims in 2012, though they are 35% of the populace. Young black men in New York are 36 times more likely to be murdered than young white men—and their assailants are virtually always other black (or Hispanic) males.

Given such a crime imbalance, if the NYPD focuses its resources where people most need protection, the effort will inevitably produce racially disparate enforcement data. Blacks, at 55% of all police-stop subjects in 2012, are actually understopped compared with their 66% representation among violent criminals.

In other words, the disproportionate amount of blacks being stopped is consistent–possibly even underrepresented–with the disproportionate amount of blacks as violent crime suspects.

When stop-and-frisk critics decry the amount of blacks being stopped, they never provide an answer as to what the proper stop rate should be. Mac Donald pinned down a leftist professor on this in August:

4. A U.S. district judge declared stop-and-frisk to be unconstitutional in 2013. The judge, Shira Scheindlin, ruled in Floyd v. City of New York and Ligon v. New York that stop-and-frisk discriminated against minorities, and was therefore unconstitutional.

But as Mac Donald explains in her book The War On Cops: How the New Attack On Law and Order Makes Everyone Less Safe, Schendlin based her ruling off the research of Professor Jeffrey Fagan, which was flawed for the following reasons:

  • Fagan did not include the race of criminal suspects in his analysis.
  • His own research found that only six percent of police stops were unlawful.
  • Fagan did not distinguish between gang homicides and domestic homicides, which is important because domestic homicides are not usually the cause of street stops. Most homicides committed by whites fall in the former category, so by not distinguishing between the two, Fagan's data model creates the impression of an anti-black bias.
  • Fagan also didn't understand the purpose of Impact Zones, where the city would put in high numbers of rookie cops in high-crime neighborhoods, which typically were minority-dominated communities.

Therefore, Fagan's data models purportedly showing discrimination against minorities as a result of stop-and-frisk can't be taken seriously, and yet Judge Scheindlin used it to strike down stop-and-frisk.

New York City Mayor Michael Bloomberg appealed the ruling at the time, but his successor, Bill de Blasio, dropped the appeal.

5. Since stop-and-frisk is no longer used in New York City, crime has subsequently increased. According to Mac Donald, in "the first half of 2015, as pedestrian stops in the city plummeted, homicides rose 20 percent; gun crime was experiencing its first two-year consecutive increase in nearly two decades." The NYPD had to put down the increase in gun crime by devoting mass resources to "crime hot spots."