Dash Cam Evidence

My understanding is that it is common practice in many (most?) police forces that the dash-cam evidence be used by the officer to create an official written report of the offense, and then the tape is willfully and intentionally deleted, since it could contain evidence that could call into questions the actions of the officer.  I find this repugnant, yet I understand it has been upheld, provided the video evidence was destroyed as a normal and routine event in accordance with departmental guidelines.  

Here is one case where the dash-cam evidence of police abuse set aside felony charges against a civilian and caused Canton police officer Daniel Harless to be fired, for many abuses and a pattern of that behavior that seems to have been documented via video several times:  http://www.ohio.com/news/local/canton-fires-verbally-abusive-police-officer-1.254697

Here are a few videos showing the offense, interesting watching - note lots of F-Bombs here, NSFW: 

This video starts several minutes into the police stop, after the driver had tried repeatedly to tell the officers searching the back seat that he was legally carrying a firearm as a licensed CHL holder: http://www.youtube.com/watch?v=UkHQuyEQze4

Long version of same, showing the complete stop  http://www.youtube.com/watch?v=kassP7zI0qc

Harless busted again for issuing death threats during police stop: http://www.youtube.com/watch?v=GpC3-2ATmIo

This is the kind of thing the FOP lobbies against, and one of the reasons video evidence is routinely erased.