In R. v. Males [1961] 3 W.L.R. 1297, the Court of Criminal Appeal was concerned with the effect of section 12 of the Criminal Procedure Act, 1851, upon the common law doctrine of merger in its application to the misdemeanour of attempt. This doctrine of the common law is to the effect that if the acts of an accused person constitute both a lesser crime and a greater, the lesser crime (at all events if a misdemeanour) merges in the greater (at all events if a felony), and is extinguished by it. In consequence, if the accused was charged only with the lesser crime, he was at common law entitled to an acquittal. Thus, in the old case of Harmwood (1787) 1 East P.C. 411, the accused, who had been indicted for an assault with intent to rape, had to be acquitted when it was found that rape had actually been accomplished.

Although revered by counsel in a case in 1851 as “ancient well established doctrine,” the principle of merger has had a fitful and at times precarious life. Its justification has never been clearly formulated, nor its province determined. Its application is in some respects arbitrary. It applies to the misdemeanour of attempt, which is held to merge in the completed crime, but not to the misdemeanour of conspiracy. It remains uncertain whether one misdemeanour may merge in another, although merger in this case was doubted in R. v. Males.

The doctrine of merger is supported by the sound reason “that no man is to be harassed by frequent prosecutions for the same offence,” as counsel expressed it in R. v. Button (1848) 11 Q.B. 929, but has in the past earned some disrepute for the opportunities of escape offered to accused persons who, having committed both misdemeanour and felony, succeeded in evading conviction of either.