Considering we know that police frequently lie in their reports doesn't that seem like a problematic source?
That doesn't mean this research has no value, but I would be very hesitant to take the conclusions of this paper as being particularly solid when it counterdicts prior research and is based off a source that we know is almost certainly biased.
I want to respond to this Churchill style. The only source less reliable than cops are all others. Cops lie, but usually its everyone else that lies more. We should take a grain of salt when anything is said. We should look for evidence to support statements.