The legal systems of the vast majority of the Black African countries can either be reckoned among the common-law family of English origin or the civil-law family in its French version. This is a result of Africa's colonial past; France and England ruled the lion's share of the continent as colonies and gradually transferred their own legal systems to their African possessions. By the time most African territories gained their independence in the sixties, the European legal systems had obtained a firm footing, albeit often still applicable only to a limited extent and in a modified version of the occidental model. After independence, practically all African states maintained the legal system imposed on them by their former colonial masters; since then, they have further developed their laws on the pattern of those legal systems. One effect of this evolving state of affairs, despite all national legal peculiarities, has been a strengthening of the basic adherence of African states to the English or French legal system. On the other hand, it has widened the gap between Anglophone and Francophone countries, at least as far as legal development is concerned. In view of both long-term political goals such as African unity, and also current intra-African relations, such as trade and administrative co-operation between the states, separate legal development in Africa might become a deplorable stumbling block.

This article is concerned with the situation when, at the end of the prosecution or defence case, in a criminal trial, it emerges that the accused is not guilty as charged but that he has certainly committed a criminal offence of a similar type to the offence charged. To take four examples: A is charged with murder, malice aforethought is not proved, yet A has committed manslaughter. Secondly, A is charged with murder or manslaughter and the prosecution fails to prove that the death resulted from A's actions. A has, however, committed the offence of unlawfully doing grievous harm or assault occasioning actual bodily harm. Next, the charge is attempted murder and it fails because the prosecution cannot prove the stringent mental element (an actual, not just constructive, intention to kill), yet A has committed the offence of unlawfully doing grievous harm or of assault occasioning actual bodily harm. Finally, A is accused of theft but since the complainant consented to the taking he is again not guilty of the offence charged, but has committed the crime of obtaining by false pretences. This type of situation may arise because the evidence does not go as anticipated by the prosecution, or because the prosecutor trips up over some subtle legal point like the difference between theft and obtaining by false pretences. Without the exceptional principles which form the subject of this article, the upshot would be that (after the expense of a trial) the accused would go free although he had clearly committed a crime.