Mr Ree,
You say 'guilty (as admitted) client....', if a client admits his guilt a barrister cannot defend him upon a not guilty plea unless
(i) his admission does not in fact amount to the commission of the relevant offence in law ie "well I'm guilty because I did X but I did not intend Y" where Y is a necessary ingredient of the offence. or,
where
(ii) there is insufficient evidence upon which the client could be convicted of the offence charged.
In the latter case we can only put the prosecution to proof and not assert a positive case to try and prove innocence.
Actually we are a pretty honourable profession who largely stick to the rules - to be honest most of us don't believe that its worth being struck off by breaking the rules. I appreciate most people have an inate mistrust of lawyers and the question we are always asked is "how can you defend people you know are guilty?" The question nobody ever asks is "how can you prosecute people you know are innocent?".
If you really want to see how the legal system works why not come along and see, if you fancy swopping a jump seat ride for a day in court drop me a line.