I'm a member of The League Against Cruel Sports and we were talking about this at the AGM on Saturday. It's difficult to get video of whoever carries out the cruelty. Even once you have that evidence, wildlife crime or any crime against animals is very low priority and is only going to get lower with police numbers being cut. That is why the league started up a department that actually do all the work and virtually hand over the ready made case to the police.
They were also saying that wildlife crime figures don't get recorded in their own category. So when it comes to setting a budget, manpower etc for this area they have no figures. So it always considered a low priority. I'm not sure if this is the same with domestic animals but it wouldn't surprise me.