“[3] Moreover, and importantly, in some instances a degree of active involvement by the police in the commission of a crime is generally regarded as acceptable. Test purchases fall easily into this category. In Director of Public Prosecutions v Marshall[1988] 3 All ER 683 a trader was approached in his shop in the same way as any ordinary customer might have done. In breach of his licence he sold individual cans of lager to plain-clothes police officers. In Nottingham City Council v Amin[2000] 1 WLR 1071 a taxi was being driven in an area not covered by its licence. The driver accepted plain-clothes police officers as fare paying passengers. Police conduct of this nature does not attract reprobation even though, in the latter case, the roof light on the taxi was not illuminated. The police behaved in the same way as any member of the public wanting a taxi in the normal course might have done. Indeed, conduct of this nature by officials is sometimes expressly authorised by Act of Parliament. The statute creating an offence may authorise officials to make test purchases, as insection 27 of the Trade Descriptions Act 1968 . [4] Thus, there are occasions when it is necessary for the police to resort to investigatory techniques in which the police themselves are the reporters and the witnesses of the commission of a crime. Sometimes the particular technique adopted is acceptable. Sometimes it is not. For even when the use of these investigatory techniques is justified, there are limits to what is acceptable. Take a case where an undercover policeman repeatedly badgers a vulnerable drug addict for a supply of drugs in return for excessive and ever increasing amounts of money. Eventually the addict yields to the importunity and pressure, and supplies drugs. He is then prosecuted for doing so. Plainly, this result would be objectionable. The crime committed by the addict could readily be characterised as artificial or state-created crime. In the absence of the police operation, the addict might well never have supplied drugs to anyone.”
“[25] Ultimately the overall consideration is always whether the conduct of the police or other law enforcement agency was so seriously improper as to bring the administration of justice into disrepute. …. ….. [28] The nature and extent of police participation in the crime. The greater the inducement held out by the police, and the more forceful or persistent the police overtures, the more readily may a court conclude that the police overstepped the boundary: their conduct might well have brought about commission of a crime by a person who would normally avoid crime of that kind. In assessing the weight to be attached to the police inducement, regard is to be had to the defendant's circumstances, including his vulnerability. This is not because the standards of acceptable behaviour are variable. Rather, this is a recognition that what may be a significant inducement to one person may not be so to another. For the police to behave as would an ordinary customer of a trade, whether lawful or unlawful, being carried on by the defendant will not normally be regarded as objectionable.”
“[113] … The judge found that the undercover officer had presented himself to Looseley as an ideal customer for a drugs deal, but the judge also found specifically that he did not go beyond that portrayal and that he presented himself exactly as someone in the drugs world would expect to see a heroin addict. There then arose a relationship between Looseley and the officer during which Looseley supplied him with heroin on more than one occasion. The judge found that there was evidence to show that Looseley was steeped in the drug culture and encouraged the officer, whom he probably saw as a lucrative customer, to take more heroin from him. [114] The judge's conclusion in the light of the facts before him was that, whilst the officer presented himself as an ideal customer so far as a drugs dealer was concerned, the officer did not do anything other than present himself as such, and accordingly the conduct of the officer did not constitute incitement. In my opinion the judge's assessment, which he made in the course of a lucid and careful ruling, was one which he was fully entitled to make.”