A Google News search for the term "sues police department," yields about 32,000 results at the moment. That would not be the number of lawsuits, but it is certainly a big enough number to consider some ways to prevent or at least keep the lawsuits honest. Many police interactions are recorded via in dash cams right now but there are some ways to supplement that footage.
Municipal security cameras can be used to monitor activities and to find out what might have really happened in a situation. These cameras provide an extra layer of knowledge and might be the only source of information should the dash cam fail or only be activated when the officers lights are turned on.
Some lawsuits happen because of negligence, but some happens because of procedure, supervisors and in the case of strong mayor towns can look over the footage to see if procedures are being followed and even to assess whether or not those procedures are valid. Police knowing that they are monitored might be more likely to follow proper protocol. In the case of frivolous lawsuits, they may be squashed before they even hit the courtroom if the footage shows other than what was stated.
With citizens armed with phones that can grab just a portion of what happened, a full scope of video footage may be useful.