"Looking at the case in the round, it seems to us that this is an unusual and special situation. The decision to defer the trial on 20 December was taken for the benefit of the prosecution in order that they would not be embarrassed when it was said in court that no evidence was being offered. The statement of the prosecution that they would offer no evidence at the next hearing was not merely a statement made to the Defendant or to his legal representative. It was made coram judice, in the presence of the judge. It seems to us that whether or not there was prejudice it would bring the administration of justice into disrepute if the Crown Prosecution Service were able to treat the court as if it were at its beck and call, free to tell it one day that it was not going to prosecute and another day that it was. Of course the circumstances of each case have to be looked at carefully, and many other factors considered... We are not seeking to establish any precedent or any general principle in regard to abuse of process. We simply find that in the exceptional circumstances of this case an injustice was done to this Appellant."
"As the judge held, circumstances can exist where it will be an abuse of process to prosecute a man for conduct in respect of which he has given an assurance that no prosecution will be brought. It is by no means easy to define a test for those circumstances, other than to say that they must be such as to render the proposed prosecution an affront to justice. The judge expressed reservations as to the extent to which one can apply the common law principle of 'legitimate expectation' in this field, and we share those reservations. That principle usually applies to the expectation generated in respect of the exercise of an administrative discretion by or on behalf of the person whose duty it is to exercise that discretion. The duty to prosecute offenders cannot be treated as an administrative discretion, for it is usually in the public interest that those who are reasonably suspected of criminal conduct should be brought to trial. Only in rare circumstances will it be offensive to justice to give effect to this public interest. 51. Such circumstances can arise if police, who are carrying out a criminal investigation, give an unequivocal assurance that a suspect will not be prosecuted and the suspect, in reliance upon that undertaking, acts to his detriment."
"These authorities suggest that it is not likely to constitute an abuse of process to proceed with a prosecution unless (i) there has been an unequivocal representation by those with the conduct of the investigation or prosecution of a case that the defendant will not be prosecuted and (ii) that the defendant has acted on that representation to his detriment. Even then, if facts come to light which were not known when the representation was made, these may justify proceeding with the prosecution despite the representation."