Strictly speaking, it was submitted that each boy's evidence was inadmissible in considering the other charge. This is somewhat surprising, since, of course, in that event there should have been separate trials .
Lord Cross of Chelsea (at 459) dealt with the matter rather more fully. He said:
When in a case of this sort the prosecution wishes to adduce "similar fact" evidence which the defence says is inadmissible, the question whether it is admissible ought, if possible, to be decided in the absence of the jury at the outset of the trial and if it is decided that the evidence is inadmissible and the accused is being charged in the same indictment with offences against the other men the charges relating to the different persons ought to be tried separately. If they are tried together the judge will, of course, have to tell the jury that in considering whether the accused is guilty of the offence alleged against him by A they must put out of mind the fact - which they know - that B and C are making similar allegations against him. But, as the Court of Criminal Appeal said in Sims [1946] KB 531 at 536, it is asking too much of any jury to tell them to perform mental gymnastics of this sort. If the charges are tried together it is inevitable that the jurors will be influenced, consciously or unconsciously, by the fact that the accused is being charged not with a single offence against one person but with three separate offences against three persons. It is said, I know, that to order separate trials in all these cases would be highly inconvenient. If and so far as this is true it is a reason for doubting the wisdom of the general rule excluding similar fact evidence. But so long as there is that general rule the courts ought to strive to give effect to it loyally and not, while paying lip service to it, in effect let in the inadmissible evidence by trying all the charges together.
Lord Wilberforce expressed a similar view, at 442. Although, as I have said, the case concerned homosexual offences, the reasoning of Lord Cross of Chelsea is equally applicable to heterosexual offences since in those cases the risk of prejudice will be equally great. In Sutton (a case arising under the law of South Australia) this Court applied the same principle to cases of rape. In that case I said (at 531; 333):
Before us it was accepted by counsel for the prosecution that where an accused is charged with a number of sexual offences, the charges should not be tried together if the evidence on one count is not admissible on another count. That was the view taken by the majority of the House of Lords in Boardman and it is a view consonant with justice .
Brennan J (at 541-542; 340-341) said:
When two or more counts constituting a series of offences of a similar character are joined in the same information, a real risk of prejudice to an accused person may arise from the adverse effect which evidence of his implication in one of the offences charged in the indictment is likely to have upon the jury's mind in deciding whether he is guilty of another of those offences. Where that evidence is not admissible towards proof of his guilt of the other offence, some step must be taken to protect the accused person against the risk of impermissible prejudice. Sometimes a direction to the jury is sufficient to guard against such a risk; sometimes it is not. Where a direction to the jury is not sufficient to guard against such a risk, an application for separate trials should generally be granted.
This is a general statement, not limited to sexual cases, and so viewed I respectfully agree with it. Sexual cases, however, are peculiarly likely to arouse prejudice, against which a direction to the jury is unlikely to guard. For that reason, I adhere to the view which I expressed in Sutton.