Violent crime and property crime drop in areas where blighted homes are razed in Detroit — and the more vacant, dilapidated houses that come down in an area, the greater the crime reduction.

That's according to a study done by two Wayne State criminologists who examined nearly 9,400 home demolitions throughout the city over a five-year period. The study, published in the peer-reviewed Journal of Criminal Justice, provides the first data-driven examination of the connection between the city's massive demolition program and its impact on crime.

Matthew Larson and Charles Klahm IV, associate professors in Wayne State's Department of Criminal Justice, reviewed 9,398 demolitions completed by the city from 2010 to 2014, then looked at violent and property crime statistics from 2009 to 2014 in the same locations down to the "block-group" level, a U.S. Census Bureau designation equating to a group of five to 12 city blocks, usually contiguous, that contain between 600 and 3,000 people.

Their findings: For roughly every three demolitions completed in that time period, block-groups experienced an average reduction in crime of almost 1 percent. With the average block-group in the study experiencing about 10.7 demolitions during that span, the average reduction in crime was approximately 3 percent.

And more than a third of the block groups had more than 10 demolitions — some with more than 100 houses razed — meaning they were likely to have a far greater average reduction in total crime.

"Depending on the type of crime, we’re talking dozens, if not more than 100, fewer crimes in a block-group, specifically tied to demolitions," Larson said.

But curiously, the study found no connection between a reduction in drug crimes and blighted home demolitions, something the researchers can't yet explain.

It doesn't appear from the crime data that removal of crime in one location has led to an increase in crime in other, nearby areas, Larson said.

The findings mirror the experience of Barb and Joe Matney, who live in a Warrendale neighborhood near Auburn Street and Whitlock Avenue, east of Evergreen Road and south of Warren Avenue. In about a one-block area near their house, for years, at least 10 vacant houses fell into serious disrepair, including the burned hull of a house that sat, unremoved, on a nearby corner.

"While the houses were still up, it was a nightly thing to hear gunshots," Barb Matney said.

Added Joe Matney, "We used to clean up the street and we'd find bullet casings all through here. There were just countless shootings all the time — some of them were even murders here — until we started this."

The city razed most of the blighted houses in the area, and the Matneys created a nonprofit organization in 2015, bought eight of the house lots from the Detroit Land Bank for $100 each, and have created a community garden at the corner of Minock Street and Whitlock Avenue. "Those who come and volunteer can take what they need for their family — the surplus goes to local food banks and pantries," Barb Matney said.

On the other side of the street, the burned-out eyesore is razed, the property cleared and a playground is planned for installation later this year.

"When we first started this, people didn't know what we were doing," Barb Matney said. "They would drive by, slow down and stare. Then, they started to wave. And then we noticed people were starting to sit on their porches again. And their blinds were up. The kids were outside playing.

"We all know crime doesn't like to be seen. So long as it's open, you're getting rid of the threat. There's nowhere for these guys to hide."

At Longacre Street and Schoolcraft, Aaron Slaughter said the demolitions have made a difference. Slaughter, 71, is president of the Longacre Block Club, a neighborhood watch group that's part of the larger Schoolcraft Improvement Association.

"We had drug dealers, we had rapists, we had all kinds," he said. "You think of the bad of the bad, we had them. But the demolition program coming about, it made it safer in the community and the neighborhood."

Detroit's demolition program is the largest in the country by far, with nearly 17,000 blighted homes razed to-date since the infusion of federal Hardest Hit Fund dollars beginning in 2010. That's only put a dent in the city's unprecedented vacant, crumbling house problem, with more than 55,000 structures still standing that are eyed for demolition. Overall, the program is expected to need more than $500 million.

The city's demolition program has seen problems in recent months — with a large demolition contractor accused of improperly burying building materials at demolition locations, and other contractors found to have used contaminated soils as backfill at house demolition sites in the city.

City officials took great interest in the Wayne State study's findings.

"This study validates our efforts over the past five years to accelerate the removal of blight from our neighborhoods," said Alexis Wiley, chief of staff for Mayor Mike Duggan.

"Detroiters have known for too long that vacant homes can become havens for the kinds of criminal activity that destroy their quality of life and pose threats to their safety."

Detroit Police Department Assistant Chief David LeValley said that while his department has not to-date looked at crime data compared to demolition data in the way the Wayne State researchers did, he is not surprised by their findings.

"When you take away dangerous buildings, or buildings that create spaces for predators to hide or commit crimes, places for drug houses to exist, because those buildings aren't being monitored or controlled, that type of action causes crime to flourish," he said.

"The cleaner an area is, the less blight there is, the less abandoned buildings, the less opportunity" for crime.

That helps the department, LeValley said.

"It's less of a resource commitment for us, where we can focus on our other crime-reduction strategies — closing cases, spending time on our investigative efforts, not having to continually patrol areas that are dilapidated or have abandoned buildings to pay attention to."

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The findings of the Wayne State research open up many additional avenues of study, Klahm said. Are the crime reductions after blighted home removal permanent, or do they diminish over time? Why did drug crimes see no perceptible impact from home demolitions, as opposed to violent and property crimes? Why did block groups that had a low number of demolitions, one to five, actually see a larger reduction in total crime than did moderate or high numbers of demolitions, six to 20 in a block group — with the crime reduction then again improving under areas with more than 20 demolitions?

"The simple answer is we do not know for sure," he said. "There is the possibility that after a certain number of demolitions there are diminishing returns until another threshold is reached."

While both Klahm and Larson said their findings might be useful to policy-makers in other cities with blighted, vacant home problems, the much larger scale of Detroit's problem and program might not necessarily produce similar crime reduction results. And both researchers noted there are other issues to consider, including gentrification in neighborhoods.

"If another city had a high rate of vacancies, that doesn’t necessarily mean that our findings suggest they should just go in wholesale and raze them," Klahm said.

Klahm also sees opportunities to study impacts for residents' well-being, pre- and post-demolition in their neighborhoods, measuring neighbors' interaction with one another, gauging mental health improvements when they're no longer "seeing these chronic, stressed properties and blighted structures on a repeated basis.

"We have a much grander vision for this project than just what we initially have done."

Contact Keith Matheny: (313) 222-5021 or kmatheny@freepress.com. Follow on Twitter @keithmatheny.