Ian Carter was arrested and sent down for stealing videos from Huddersfield nick relating to sexual offences. He was found to have illegal material in his home which he had taken from the police station using USB pen drives. Presumably, he could also have destroyed, fabricated, and otherwise tampered with evidence; therefore, anyone who has submitted evidence to Huddersfield Police might have had their evidence stolen or modified (the same rule applies to the evidence recovered from Carter’s cache, and evidence taken by the police from inside peoples homes).
This means that all evidence submitted by Huddersfield Police is suspect. They quite possibly have a ring of paedophiles working from their police station.
Also, because Carter was using his computer to store illegal images involving children and animals, he was quite possibly a member of illegal (in the UK) websites, and probably shared the material he had taken with the other members.
Given the time and effort it takes to gather such evidence, it is a travesty to see it being abused in this fashion. It also explains why so little evidence makes it to the courts. Even if he worked alone, which I doubt, he has done untold damage.
Another factor is the recent disclosure that USB devices can easily be hacked. The machines at the station could easily become infected with BadUSB, and Carter, wittingly or otherwise, becoming the distribution vector by transporting the drives between his home and the Huddersfield Police Station.