By Suzanne Le Mignot

CHICAGO (CBS) — Part of Chicago’s plan to stop a spike in gun violence includes massive overtime by police. But will longer workdays really lower crime?

A police expert told CBS 2’s Suzanne Le Mignot longer hours for officers can make a difference, but there’s a lot more involved when it comes to preventing crime.

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On Monday 21 people were shot and three killed in Chicago. Tuesday eight people were shot in a mass shooting at a home in Englewood, located in the Englewood (7th) Police District. Four of those people died. The same day five more people were shot in the Harrison (11th) District.

David A. Harris gave said not all the violence can be stopped. He gave that perspective when it comes to longer hours for officers and mass shootings in the city. Harris is a professor of Law at the University of Pittsburgh School of Law, specializing in search and seizure law and police conduct.

“Simply by having more police boots on the ground, if you have a shooting inside a home or another kind of building, there typically won’t be police presence,” he said.

Harris said this short term strategy of 12 hour work days for officers can be a plus.

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“A greater need for more people, you can achieve that in the short term by increasing the hours they work.  You just have more of them around for longer periods of time.”

Two of these mass shootings were in districts where CBS 2 has learned 12 hour days started for officers Tuesday on the third watch, an afternoon shift. In nine South and West side districts, officers on the second watch, or morning shift, will also be working 12 hour days, until further notice. Those districts are: Wentworth (2nd); Grand Crossing (3rd); South Chicago (4th); Calumet (5th); Gresham (6th); Englewood (7th); Ogden (10th); Harrison (11th); and Austin (15th).

Sources with direct knowledge of the situation say the increase in manpower in these districts was based on data and crime patterns. Harris said a bigger police presence can be a benefit when it comes to large gatherings.

“It will allow police to respond much more quickly because there’s simply more of them and they’re closer by,” he said.

He said the bottom line is police must work to build relationships with those in the communities they serve. That’s not done through traffic stops, but through building a relationship of trust. But he said that takes time.

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Beat officers to brass are exhausted across the board, but Harris said hiring more officers is not the answer. Data shows it is building those connections with the community that really works and can lead to crime prevention.

Suzanne Le Mignot