Plenty of knuckle dragger's who ought to not have responsibility for anything, let alone the care and despatch of live animals.
As for the evidence being 'inadmissible' well, that smacks of semantic BS to me - there may well be an animal rights bias, but that doesn't mean some of the actions described are not plain wrong.
I know a chap who works in a knacker yard, dealing with all sorts of farm animals (lambs, sheep, pigs, calves, cows. bulls, horses the lot). He takes the business of killing them very seriously indeed. There's no complacency or cruelty or distress caused to the animal (you can tell when a horse is agitated by unfamiliar surroundings), they are led off horse box, walked across the yard and then shot immediately.
Seeing it done like that you get to see how much care and attention is taken even though the time-scale involved is very small - that's part of the process of keeping the animal calm and not delaying the process.
Part of the problem here is the industrial scale of it all. But that shouldn't mean needles cruelty is acceptable.
The discussion of the use of CCTV is an odd one given that there's been cameras watching staff in every goods warehouse I've ever worked in over the last 15/20 years, one would question why some companies don't have it installed already, and those that do have it, how they have not picked up these kinds of unacceptable actions before now? My guess is they know it goes on, but just ignore it.