You say that it has been proven in court, can you post a link or reference to qualify that statement please?
I'm afraid as previously stated, you are wrong.
Cats are classified as property, and their owners are not legally responsible for their actions.
As for checking each cat you think is feral; it is not a legal requirement, but is 'best practice' and has been used in court.
Please note,i am NOTE trying to start an argument,purely putting what others WILL be thinking>
As a terrier owner,does that also mean i am NOT legally responsible for my terriers actions 'SHOU