No need to plant evidence when you can just change the database entry to match the evidence that you've found.
But how would your average, or even well above average Garda get write access and change DB records and cover up the standard record versioning history? I have DBAs with 15+ years experience that couldn't do that to internal databases we have that aren't exposed to the internet, or hold data that anyone external would be interested in.
Why isn't this happening wholesale with fingerprints?