In Muslim jurisprudence there was no really complete system of criminal law. The basis being religion, the concept of crime merges with the concept of sin. In comparison with Roman-Byzantine law, Fiqh in consequence wears a strangely antiquated look. For example, the subject of law is not the person but the family; murder is regarded not as an offence against society, but as an offence against the family of the victim. The Shari'a retained the vendetta and it retained the 'blood price' which we meet with in the Russkaya Pravda or 'Russian Right', that earliest document of our own law, under the name of vira, and also in the legal systems of barbarous Western Europe, under the name of wergeld, from the fifth to the ninth centuries,that is, until feudalism had developed. The features of Fiqh here listed are survivals from the clan- and tribal-custom of pre-Islamic pagan Arabia; in other words, remnants of a patriarchal order which Arab society clung to when it entered the feudal phase. As against this, many other features of the criminal system of Islam were far in advance of the legislation obtaining in Western Europe, not only under the full feudalism of the eleventh to fifteenth centuries but even under the absolutism of the sixteenth to eighteenth centuries. Thus, according to Fiqh, only the adult, the mentally sound and the free can be fully answerable for a transgression; minors, the mentally sick and slaves are not responsible or have a limited responsibility. Muslim law does not allow the use of torture (which several European countries employed as late as the eighteenth century) nor does it countenance 'the divine decision' whether in the shape of the ordalia, the ordeal by fire and water, or of the legal duel between plaintiff and respondent, as practised in Western Europe and Russia in the Middle Ages. It does not tolerate, or very exceptionally, a lengthy term of imprisonment. Its criminal procedure was marked by speed and expedition and was innocent of the judicial delay, sometimes amounting to years, and the consequent ruinous costs, which characterized European and Russian courts even in the last century.
In its family and marriage regulations the Shari'a retained certain items of the patriarchal clan system of old Arabia. One of these was the obligation of the bridegroom (or else his relatives or guardian) to pay the bride a marriage settlement called mahr. This is done by formal engagement, the amount being either fixed à l'amiable (in which event it was mahr musamma, 'named settlement') or the same as that received by other girls and women of the bride's family at the time of their marriage (in which case it was mahru 'l-mithl, 'settlement after the example'). The actual sum varies greatly, depending on the financial status of the bridegroom's family; but more is, as a rule, expected for a virgin bride than for a woman who has been married once or several times before. The marriage portion becomes the bride's own propertynot that of her family; there is here a departure from pre-Islamic custom under which it was payable to her clan so as to compensate it for the loss of a girl.