Looks like he was originally going for the defence of not knowing he had the weapon in his possession. Going from memory, it for the Prosecution to show that the person actually knew of the item and that it was in his possession. By saying his mates had packed his container and he hadn't opened it, he was saying didn't know he was in possession of the weapon.
In a previous job, I saw a number of cases of drug and offensive weapon prosecutions dropped over that same argument e.g.
- machette found in a car - must have been left by the previous owner
- spliff found in a coat pocket whilst being worn by the person - must have put there by someone who borrowed the coat earlier in the evening
- 1 spliff in a car, 4 occupants, no one would admit to it being theirs and no way to tie to one person...
But by pleading guilty, he has admitted he knew the weapon was in the container or he was advised that his not knowing was not going to be accepted. Perhaps his defence was advised that he should change his plea. Agree that it was harsh sentence especially when compared to what some
get for violent crimes.