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[jamz]

...my son....

This seems reasonable, since it's obvious there are two of you playing at the same time.

As the "Skilly, P," he denies having hacked credible.

I'm sorry, but he has cheated again. If you watch the demo, you can see quite clearly how his aim moves very quickly from red player to red player, always going immediately on target.
To play a demo, save it to your /demos/ folder in your AssaultCube folder. It will then be available in-game through the Demo menu.
Unfortunately, I cannot allow you to play and still keep your son banned. I'm very sorry that this has affected your enjoyment of the game, and I hope your son learns a lesson from this.
The usual punishment for a second offence is a permanent ban. I think there will be some discussion here about this case, and I will make a decision based on what I read.