Study says: Police Body Cams Have No Effect. I Expected This

You have cops everywhere doing cop things. Every now and then a cop does something really bad and someone gets killed. That is not going to show up as a statistical effect when looking at the overall behavior of the cops, unless you do some very specialized Bayesian statistics, which no one is going to do on that sort of data.

So, the just released study, summarized here by NPR, is not a surprise.

Having police officers wear little cameras seems to have no discernible impact on citizen complaints or officers’ use of force, at least in the nation’s capital.

That’s the conclusion of a study performed as Washington, D.C., rolled out its huge camera program. The city has one of the largest forces in the country, with some 2,600 officers now wearing cameras on their collars or shirts.

“We found essentially that we could not detect any statistically significant effect of the body-worn cameras,” says Anita Ravishankar, a researcher with the Metropolitan Police Department and a group in the city government called the Lab @ DC.

“I think we’re surprised by the result. I think a lot of people were suggesting that the body-worn cameras would change behavior,” says Chief of Police Peter Newsham. “There was no indication that the cameras changed behavior at all.”

Perhaps, he says, that’s because his officers “were doing the right thing in the first place.”

The purpose of the body cam is to find out what happened in this or that extreme event, when there is a death, or a plausible accusation of wrong doing. Another likely effect of the body cam is to cause bad behavior to be more rare, just because the cameras are there. But bad behavior is often the result of out of control emotions, or of bad training, or some other thing that the presence of a cam is unlikely to detect. I would not be surprised if body cams did have this effect on some police forces, but not most.

There are statistical ways to see if the body cams are having an effect on behavior but they have to assume that the behavior is a) really there already and b) of a certain specific form. Then you can subset your data down to the sensitive parts of it, and see if, say, before or after body cams you get a difference. But really, the best way to do that is to pair up the cops (statistically) so you have one set of cops match, with respect to relevant characteristics, another equal size set (on the same police force) where one set is wearing the cams, the other not (there are some added difficulties in doing this, like matching patterns so neither or both have the cams, etc). This sort of approach could identify an effect. But the methods that would normally be used won’t unless it is dramatic.

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13 thoughts on “Study says: Police Body Cams Have No Effect. I Expected This

  1. unless you do some very specialized Bayesian statistics

    Possibly. The real issue is that the nasty occurrences, while happening far too often, are still a very small fraction of all the interactions officers have. Extremely rare events are difficult to find (which is part of the reason an occurrence makes big news) — this is the same issue with “good guys with guns stop a crime” — and that rarity makes them exhibit nothing more than a tiny blip statistically.

    But really, the best way to do that is to pair up the cops (statistically) so you have one set of cops match, with respect to relevant characteristics, another equal size set (on the same police force) where one set is wearing the cams, the other not (there are some added difficulties in doing this, like matching patterns so neither or both have the cams, etc).

    Or look back with a case/control study. The difficulty with that is sorting through all of the
    sources of bias in the gathered responses.

  2. Dean, exactly. One way to try to measure differences here would be to narrow down the question of what one is looking for to be very finely tuned.

    I was thinking of case/control as well.

  3. I was thinking of case/control as well.

    I was 98\% sure of that, but was holding out just a bit in case you had something else in mind.

    I would be interested in seeing the rate of non – compliance with these camera laws: is there an association between departments with concerning records of behavior and officers “forgetting” to have the camera on? How about the other way: departments with very good records and the rate at which officers do have the camera on? That data might be much easier to get.

    1. Exactly. There is some evidence that turning the cams off is a thing. Also, police unions are very nice to cities by insisting that always on will use up too many resources for the city, so let’s not do that!

  4. I think that control of the body and car cams should be done by another agency. There have been a number of cases (no actual data other than reading articles) of body or car cams being off when something bad happens. If the officer or department can control the on off function, then the cameras become more a cya tool than a tool see or prevent police from doing the wrong thing. Also, if the camera is off, what the other party is doing is unknown whether good or bad.

    1. That would help in some cases. But even in the case of third-party control, if an officer really wanted the camera to stop recording, a plausibly excusable way to accomplish that would be found.

      Also, many police unions would accuse the third party of anti-police bias.

  5. If the officer or department can control the on off function, then the cameras become more a cya tool than a tool see or prevent police from doing the wrong thing.

    Partially agree — leaving control of the cameras to the officers is a weak link, but I think having it in the hands of a third party would complicate things immensely (and would lead immediately to questions of privacy for the officers, with the “film” being in control of the third party). And I’m not sure the thought is that these cameras will prevent anything: I can imagine the likelihood is for the officers predisposed to extremes will either react without thinking, or will deactivate the camera first, act, and claim it was damaged during the confrontation.

    Also, if the camera is off, what the other party is doing is unknown whether good or bad.

    True, but this should be an enticement for most officers to keep the camera on, as it would provide evidence to support any claims of resistance or attack from civilians.

  6. Dean, at least to me, while a officer is on duty (breaks are not duty time) they have little entitlement to privacy. Therefore, what they see, say, hear or do while on duty is public domain. Cameras are at least one tool to try to keep officers within the bounds of the law.

    Having a third party, whether within or outside of the PD would hopefully prevent abuse of the camera systems.

    As you said having the camera on also protects the officer from accusations of abuse that are not truce.

    Other than in your own home, I don’t know if the right to privacy really exists anymore with the number of cameras located everywhere. With devices such as Echo, I am not sure, at least with sound, privacy in your home exists now.

  7. Dean, at least to me, while a officer is on duty (breaks are not duty time) they have little entitlement to privacy. Therefore, what they see, say, hear or do while on duty is public domain.

    Possibly — hadn’t thought about that.

    I don’t know what Amazon does with the data collected from their Echos — I don’t have one and don’t have an Amazon account for anything. I do have a Google Home, and Google is quite clear with what they do with your data — selling it isn’t on the list, and they would be stupid to do that, since it’s worth far more to them for crafting ads to you than it would be to sell. I think Apple follows roughly the same guideline.

    But worrying about those devices collected data is a little late — especially if you’ve had a smart phone (or even a cell phone before that) for any length of time.

  8. Dean, I think my point is that privacy as we once knew it is long gone. How we adapt to living in this type of environment is an interesting question.

  9. There is no doubt about that. Scarier to me though, are feeling demands by government to have companies turn over custom data. One of the cases the supreme Court is reviewing involves the DOJ and Microsoft. The DOJ wants to be able to see data from customers in other countries — their argument is basically that Microsoft is a United States company so it has to follow US law regardless of where its clients live.

    As a politician in Germany recently said, we’re one terrorist attack away from losing our right to anonymity.

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