I did equine related litigation for many years. I'm just telling you how it would probably shake out.
May not like it, may not think it's fair, but that's the way it is.
Because of the perceived unfairness of the legal situation, in Georgia an "Equine Immunity Statute" was enacted a number of years ago. It's been thoroughly litigated and has stood up pretty well -- but there is still an exception where the owner of a horse has concealed or failed to disclose an unusual vicious propensity.
As a general rule, it doesn't fly with experienced horsemen, because of the provisions of the immunity statute. For example, I could never sue anybody for an injury I incurred, I've been riding too long and I'm too well aware of all the things that can go wrong.
About the only way an experienced horseman can sue is a situation that I was involved in probably 20 years ago, where a stallion was sold at a sale while Aced up within an inch of his life . . . and then nearly killed the purchaser when the sedative wore off. That was of course a claim for fraud etc. and the plaintiffs got a big judgment.
So if you know all that... why did you say you'd take some as-yet-unknown plaintiff's case?