What pre trial work does a Barrister QC undertake with the defendant, if a defendant has only given a vague statement to the police to what extent can the Barrister elaborate on that, can he gain a full account from his client above the statement and defend without putting the defendant in the dock.
Any statement that the defendant makes (whether to the police or anybody else) can only be put before a court and "read" (that is, read out without the defendant having to answer questions about it) if the prosecution agrees. If they do not, then the defendant will have to give evidence under oath or affirmation as a witness and be subject to cross-examination.