The null finding may be real.
It may be the case that BWCs do not, in fact, affect the measured behaviors and the video footage does not affect the measured court outcomes.

To unpack this possible explanation a little further, we also conducted a time-series analysis (see the Working Paper) that tracks both the treatment and control groups over time. This analysis allows us to consider whether, for example, strong initial effects may have dissipated as officers became accustomed to the cameras. We find, however, that control and treatment group behaviors track closely together, both before and after the deployment of BWCs.

There may be minimal misconduct to improve upon.
BWCs might help improve behavioral outcomes in departments with notable misconduct issues. However, the elevated scrutiny MPD encounters as the police force for the capital city, combined with substantial reform efforts over the past twenty years, may have helped mitigate these types of issues at MPD, limiting the added effect of BWCs.

There may be an effect, but it is hidden.
MPD operates in an environment already saturated by cameras, which may limit the added effect of BWCs. Three potential ways this may occur (not mutually exclusive):

• Direct spillover of BWC presence: a control officer without a BWC may be affected by his or her awareness of a nearby colleague in the treatment group who is equipped with a BWC.
• Indirect spillover of BWCs via training and culture: the introduction of BWCs into MPD may have caused a shift in the norms of the broader force even though devices were only deployed to a subset of the officers.
• Saturation effects caused by the widespread presence of non-police cameras: Civilians regularly record encounters with MPD members with their own cameras, and CCTV is widespread. It may be the case that these existing cameras affect behavior to the extent possible, and adding BWCs into the mix has no discernable marginal effect.

There may be a policy adherence issue:
The cameras would have an effect if used according to MPD policy, but they may not be used properly (e.g., officers not turning them on). For 98% of the days in 2016, MPD averaged at least one video (and often many more) per call for service associated with a treatment officer. Even for the 2% of days in 2016 in which the number of videos uploaded was less than the number of incidents for which we would expect them, the difference was minimal, with 96% average compliance based on our measure. We conclude from these statistics that policy adherence was likely high.

BWCs may have an effect, but it may not be captured in administrative data:
For example, it may be the case that there were uses of force that were previously going unreported, and those have now dropped with the introduction of BWCs. But because our data do not capture unreported uses of force, we are unable to detect this kind of change.