I assume such a list would have rows consisting of, at minimum:
a. link to case's public testimony (CPT)
b. text in CPT to officer's statement.
c. text in CPT that contradicts the statement.
(I'd love to see an example row!)
2. Innocent until proven guilty? I'd say best to start with the clear lies first to build the list's credibility. However enough borderline cases surrounding an individual or department can also be interesting.
3. Defamation requires that the statements about the person be false. Referencing court docs about what they said should obviate that concern. Maybe the trick is to bill the db as a "list of inconsistencies" rather than outright lies.
4. I'd be more concerned about DoS attack rather than spam.
Hmm I like how your idea helps with both (3) as you said, and also with what I called "spam".
I had in mind a service where people were allowed to write in their claims of testilying -- how do you prevent it being "spammed" by every criminal with a grudge against a cop.
By asking them to cut and paste text from CPT -- which can then be electronically verified, you can cut down on the casual attempts. Of course a real attacker can get around that trivially.
Another question is where to host it. While truth is a libel defence in the US -- I am not sure that is true in other countries.
Unfortunately, I am unaware of any of those. It stands to reason that police officers speaking openly in this manner about lying under oath don't face repercussions and consequently don't get tracked much.
Are there public databases that track dishonest officers? That could be incredibly helpful to defence lawyers.