The notion in our legal system of advocates acting on instructions is well accepted.
Lawyers are contractually and ethically obliged to obey their client’s instructions. Indeed, they may not act contrary to their instructions. It is for this reason that generally, an accused person is bound by the way a trial is conducted by their counsel: TPC v TNT (1983) 56 ALR 647 at 662 – 4; R v Birks (1990) 19 NSWLR 677 at 685; R v Wakim  2 VR 46; R v Brown (2002) 5 VR 463. The corollary of this is that questions or conduct of counsel may be used as evidence of instructions: R v Delgado-Guerra  2 Qd R 384 at .
If their instructions are withdrawn, their retainer is ended and they no longer have any right of appearance: R v IAS (2004) 89 SASR 159; R v Greer (1992) 62 A Crim R 442 at 452.
But similarly, advocates owe an overriding duty to the court to do nothing that would obstruct the administration of justice: D’Orta-Ekenaike v Victoria Legal Aid (2005) 223 CLR 1 at 41. This gives rise to the obligations of candour, expeditiousness, and disclosure of relevant law — even if unfavourable to the client’s case. It’s also reflected in the cab-rank principle, which I discussed here in April.
We see this reflected in rules such as rule 16 of the Victorian Bar Rules, and rule 41 of the Australian Bar Association model rules, which say:
A barrister must not act as the mere mouthpiece of the client or of the instructing solicitor and must exercise the forensic judgments called for during the case independently, after appropriate consideration of the client’s and the instructing solicitor’s desires where practicable.
Rule 13.1 of the Professional conduct & practice rules 2005 (Vic) for solicitors is almost identical.
So, if the client says, “I want you to cross-examine the witnesses this way,” or, “I want to call this evidence,” and the advocate considers that they should not do so, it seems there’s a conflict between the duty to the client and to the court.
But, it really depends on what it is a client can actually instruct or direct their lawyer to do.
I challenge you to find in any of the standard texts on advocacy or ethics some discussion on what acting on instructions truly means. I went looking, for this post, and I couldn’t find much. Ysaiah Ross has a little bit in his book Ethics in Law, but not much.
But the English Court of Appeal considered the point a few years ago in R v Ulcay  1 WLR 1209.
Mr Ulcay and his co-accused were charged with and convicted of people smuggling. Ulcay was represented by two barristers and a solicitor, but they withdrew at the close of the prosecution case. Why? Up till then, Mr Ulcay had admitted that a voice on a large number of telephone intercepts was his, and that the person named on the intercepts as “Eddi” was him, Erdogan Ulcay.
But then Mr Ulcay changed his instructions. After the prosecution closed its case, he now denied he was Eddi, or that the words spoken by Eddi on the intercepts were his words, or that the voice originally admitted to be his voice was his voice. He said he didn’t want to be represented by his current lawyers. They were permitted to withdraw.
Over the next week, two new barristers appeared, Ms Tayo and Mr Aina. Mr Aina asked for a four to six week adjournment. (By then, a week had passed since the prosecution case closed, and so the jury had been spending seven days kicking their collective heels in the jury room while this all went on. You can just imagine how rapt they must have been about that.)
That application was refused. The next day, Ms Tayo and Mr Aina withdrew. Two days after that, two new counsel appeared, and asked for a seven-day adjournment. That too was refused, and the second set of lawyers withdrew. The case continued. Mr Ulcay was unrepresented.
Ulcay was convicted. He appealed, arguing the judge was wrong to allow the original lawyers to withdraw, and then to not allow the adjournment sought by the new lawyers.
The Court of Appeal rejected that argument.
 …the processes designed to ensure the fairness of his trial cannot be manipulated or abused by the defendant so as to derail it, and a trial is not to be stigmatised as unfair when the defendant seeking to derail it is prevented from doing so by robust judicial control. Such a defendant must face the self-inflicted consequences of his own actions.
 Mr Aina pointed out that in his ruling on 18th October, the judge did not expressly state that the appellant was seeking to manipulate the process of the court. Indeed he never said so. However we have no hesitation in saying that it is perfectly obvious that this is what the appellant was seeking to do, a conclusion which we would have reached independently of, but which is powerfully fortified by, the factual observations of trial counsel following the appellant’s waiver of privilege. When he was addressing these problems, it was incumbent on the judge to be more reticent. It does not need much imagination to envisage the likely response if he had suggested that the process was being abused or manipulated. It would have formed the basis for an application for a new and separate trial before a new jury and an “unbiased” judge. We shall focus exclusively on the stark realities.
 This appellant was provided with competent lawyers at public expense and given ample opportunity for the preparation of his defence. Before trial the issues were carefully addressed by him, and his lawyers, and he was then properly represented by counsel before the jury. It was a constant theme of the pre-trial preparation, and indeed of the discussions in conference while it was in progress, that counsel could only act on the basis of the appellant‘s instructions. For example, counsel made clear that he would not challenge evidence which the defendant accepted was accurate, and the fact that another co-defendant was challenging the same evidence could not justify a challenge on the appellant‘s behalf. All this seemed to be clearly understood by the appellant, at any rate until the close of the prosecution case, when his understanding appears to have broken down.
The Court then turned to what is meant by acting on instructions.
 The correct meaning of the phrase “acting on instructions”, as it applies to the professional responsibility of the advocate in any criminal court, is sometimes misunderstood, even by counsel. Neither the client, nor if the advocate is a barrister, his instructing solicitor, is entitled to direct counsel how the case should be conducted. The advocate is not a tinkling echo, or mouthpiece, spouting whatever his client “instructs” him to say. In the forensic process the client‘s ”instructions” encompass whatever the client facing a criminal charge asserts to be the truth about the facts which bring him or her before the court. Those instructions represent the client‘s case, and that is the case which the advocate should advance. In practical terms, that will often mean that prosecution witnesses will be cross-examined on the basis that they are lying or mistaken, or have misunderstand or misinterpreted something said or done by the defendant; however there is almost always some evidence advanced by the prosecution which, on the basis of the client‘s instructions, is not in truth in issue at all, either directly, or indirectly. Some decisions, of course, must be made not by the advocate, but by the defendant personally, for example, and pre-eminently, the plea itself, and in the course of the trial, the decision whether or not to give evidence. The advocate must give his best professional advice, leaving the ultimate decision to the client. It is however always improper for the advocate to seek to challenge evidence which is accepted to be true on the basis of the facts agreed or described by the client, merely because the lay-client, or the professional client, wishes him to do so. He may not accept nor act on such instructions.
The stock-in-trade manner of questioning a client charged with a criminal offence by going through the brief, and saying, “The prosecution says [this]; what do you say about [that]?” is the best way I‘ve seen for getting instructions that meet this definition, and avoid (perhaps well-intentioned) advice about how best to do my job. How have you seen others do it successfully (or not), or how do you do it yourself?
I know some folks often view with some scepticism assertions that, “Those are my instructions.” Heck, sometimes advocates even share that scepticism. We can’t coach witnesses, but we can question and test the version given to us by a witness or potential witness (including an accused). But, their instructions are their instructions, not what we think likely — really, no one cares what we think, just what we submit — and we’re bound by them.