i've said this once on a comment
But a-sheng really did the crime. I'm not defending ghostblade. But if we look at a-sheng charges which is to lie to the commission, to hide and train an unidentified being and to refuse to cooperate with higher ups.
We know that a-sheng is a good person, he's a family man at heart. But he is by law in the wrong. His personality don't matter at that point. It is very lucky that big Johnny is a cute and harmless alien. But imagine if a-sheng failed to tame him resulting in him escaping and being used as a weapon by another person.
Which is why Gb has to kill him and why he must finish this job now as big Johnny is starting to attract more attention.
Though there might be a second person involved in a-sheng situation. The question is who? Is it the lady who is said to be x ally?