Absence of evidence is evidence of tampering. It is not proof.The popular phrase "absence of evidence is not evidence of absence" is wrong. Absence of evidence is evidence of absence.
When it comes to cameras, the question in how often they fail on their own compared to how likely tampering is, and any relevant context which might modify those basic probabilities. If the demonstrated mean time between failures is 10 years and your cameras are failing on average once every year then something is going on, for example.
Your mention about punishing the officer makes me wonder if you actually read my comment, though. I explicitly suggested that a camera malfunction should not be considered sufficient to clear the "beyond a reasonable doubt" bar for a criminal case, and that while it should work for a civil case, the cost there would not be borne by the officer.
The actual popular phrase is "the absence of evidence is not the evidence of absence" and that is NOT what I was referring to. The absence of evidence is still not evidence of tampering unless tampering can be proven. A hair fiber belonging to a suspect that is found at a crime scene is evidence that the suspect was there. A lack of a hair fiber of a suspect at a crime scene is not evidence that the suspect cleaned up their hair from the crime scene. Bleach on a floor at a crime scene is evidence of an attempt to clean it up. Does that make sense?
I'd argue that body cameras have not been around in wide circulation long enough to provide any meaningful data on their failure rates. Also I can safely assume they have some sort of warranty on them but that does not prevent a handful of defective ones from making their way into active use amongst law enforcement personnel.
Civil cases, on the other hand, merely need to meet the standard of "a preponderance of evidence" to support the claim. A mysteriously malfunctioning camera ought to meet that standard, and thus be grounds for an award of damages due to misconduct.
This is the passage I was replying to and you paraphrased another user's comment regarding a default judgment in favor of the civilian if the camera malfunctions. A malfunctioning camera does not necessarily prove a deliberate tampering and to hang an entire civil case judgment on that is not giving the losing side a fair shot at winning their case. The officer is employed by the department and a judgment born by the department in reference to the officer when the officer did not do anything wrong can have adverse consequences on their career and by extension, their life, far more than you are giving credit to.
Given that BWCs (body-worn cameras) weren't even significantly tested in the U.S. until 2012 and are still not what most people would agree is considered "widespread" then we can hardly conclude much of anything about their failure rates in active use.