San Antonio Drops ShotSpotter, System not Cost Effective

Shot Spotter Sensor in Omaha, Nebraska

One of the technological fixes that has been attempted is the use of sensors to pinpoint gunshots inside of cities. The theory of the technology is fairly simple. Spread audio sensors throughout the city. Feed the input into a computer system, looking for gunshots. With sophisticated programs, isolate the gunshots from the other noise, and pinpoint their location and time. Ideally, this happens in near real time, to allow police response to gunshots. From ksat.com:

San Antonio - A program intended to help police officers identify where a shooting happens, get there quicker and ultimately cut down on crime has been stripped from the proposed city budget because city leaders said it's not effective.

It cost the city $270,000 to put ShotSpotters on the city's crime-ridden east and west sides, but police Chief William McManus said the program's results don't match up with its hefty price tag.

The experience in San Antonio shows the limitations of such a system.  The system has been in place for more than a year. That is the time the system should be most effective. The sensors are fresh and new and have not had time to corroded or broken.

In the period the the system was in place, the police obtained four arrests because of information received from the system. That does not necessarily translate to four convictions.  Another article says that the total cost of the system was $378,000 plus $168,000 for officer overtime associated with the program. So the city spent about $136,000 per each arrest.

From expressnews.com:

The four suspects were arrested on charges of discharging a firearm, a Class A misdemeanor, the SAPD’s Sgt. Jesse Salame said. One of the suspects also was charged with possession of narcotics.

There was no known shooting victim in any of those four cases, Salame said.

It is easy to see why the Police Chief McManus had questions about the usefulness of the system. While some costs would be spread out over years, the overtime and maintenance costs could conservatively be $75,000 a year per arrest. That would be most of the cost of a full time police officer, to make one misdemeanor arrest where no shooting victim was involved.

The technological costs of systems such as ShotSpotters are likely to go down; but the personnel costs are likely to increase. While the system sounds plausible in theory, in San  Antonio it has not been cost effective in practice.

In Connecticut, another Shot Spotter system was reported to have limited effectiveness. From fox61.com in 2013:

Violent criminals are small in number in all communities. Spend the resources on monitoring and apprehending those known individuals, and violent crime will decrease.

Can systems such as ShotSpotters be effective? Technological solutions to crime can be helpful, but there are always countermeasures. Criminals wear gloves to stop leaving fingerprints, or masks to foil cameras. Shots fired inside buildings are difficult to detect; sensors can be destroyed. Wind muffles and distorts sound based systems.

A major problem is the systems are reactive. They only show where an outside gun shot may have occurred.  If they report many false positives, the cost of investigating the false positives adds up quickly. They may be helpful in locating crime hot spots; it is likely that those locations are already well known.


©2017 by Dean Weingarten: Permission to share is granted when this notice and link are included.

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