The case of the headless corpse is based on one related in a Chinese casebook of the thirteenth century, translated by me under the title T'ang-yin pi-shih, Parallel Cases from under the Peartree, A thirteenth-century manual of jurisprudence and detection (Sinica Leidensia Series, Vol. X, E. J. Brill, Leiden 1956). Case 64 of that handbook says that c. a.d. 950 a merchant found the headless corpse of his wife when he returned from a journey; the wife's family accused him of having murdered her, and he wrongly confessed under torture. A clever detective had doubts and started questioning all the undertakers of the district about unusual burials. One of them reported that he had buried for a wealthy man a dead maid, but that he had noticed that the coffin was extraordinarily light. The detective had it opened, and it was found to contain only a severed head. It then transpired that the wealthy man had killed the maid, and placed the headless body in the house of the absent merchant, whose wife he had taken as secret paramour. This meager story leaves much to the imagination and contains several improbabilities, such as the merchant's not seeing that the dead body was not that of his wife; these I tried to eliminate while working out the motif for the present novel.
The nail murder is one of the most famous motifs in Chinese crime literature. The oldest source is quoted in the casebook T'ang-yin-pi-shih mentioned above, in Case 16, where the solution is ascribed to Yen Tsun, a clever judge who lived in the beginning of our era. The point of these stories is always the same: the judge is baffled by the fact that although there are strong reasons for suspecting the wife, the body of the husband shows no signs of violence. The final discovery of the nail is elaborated in various ways. The oldest version says that Yen Tsun found it because he noticed that a swarm of flies congregated on one place on top of the dead man's skull. The latest version known to me occurs in the eighteenth-century Chinese detective novel, Wu-tse-t'ien-szu-ta-ch'i-an, which I published in English translation under the title Dee Goong An (Tokyo 1949); there the judge finally elicits a confession from the guilty widow by staging in the tribunal a scene from hell which makes the woman think she is appearing before the Judge of the Nether World. Since this solution would not appeal to the Western reader, for the present novel I utilized quite another version, briefly recorded by G. C. Stent under the title The Double Nail Murders, and published in 1881 in Volume X of the China Review. When the coroner fails to discover any trace of violence on the victim's corpse, his own wife suggests to him that he look for a nail. When the judge has convicted the murdered man's widow on this evidence, he has also the coroner's wife brought before him, since her knowledge of such a subtle way of committing a murder seems suspicious to him. It transpires that the coroner is her second husband. The corpse of her first husband is exhumed, and a nail discovered inside the skull. Both women are executed.
In my preceding Judge Dee novels the magistrate always appears as the omnipotent, infallible judge who invariably gets the better of the criminals brought before him. In the present novel I tried to show the reverse of the medal, stressing the grave risks a magistrate incurred as soon as he made a mistake. It should be remembered that the magistrate's position of well-nigh absolute power and complete superiority over all persons brought before his bench was but borrowed glory, based not on his personal rank but derived solely from the prestige of the government he was temporarily appointed to represent. The law was inviolable, but not the judge who enacted it; magistrates could not claim for themselves immunity or any special privileges on the basis of their office. They were i.a. subject to the age-old Chinese legal principle of jan-tso, "reversed punishment," which implies that the person who wrongly accused another shall suffer the same punishment as the wronged person would have received if the accusation had been proved true. For this aspect of the case of Mrs. Loo, I utilized some traits described in Dee Goong An. At the same time I tried to comply with the — not unreasonable! — demand of some readers that the fair sex should play a greater role in Judge Dee's life.
As to my story of Yu Kang and Miss Liao, it should be noted that although the Chinese have always taken a very tolerant view concerning premarital sexual relations of a man, his future wife is strictly taboo. The reason is presumably that while relations with courtesans and unattached women are a man's private affair, his marriage was considered as affecting the entire family, including the ancestors, to whom this solemn act had to be reported with due ceremony. Consummation of the union before it had been officially announced to the ancestors was a grave insult to them, proving a criminal lack of piety. And since times immemorial the Chinese have classified impiety toward one's parents, whether dead or alive, in the legal category of pu-tao, "Impious crimes," which imply the death penalty in one of its more severe forms.
Ancestral worship is the cornerstone of Chinese religious life. Every family used to have its own household shrine containing the wooden tablets in which the spirits of the dead members of the family were supposed to dwell. The head of the house announced to these spirits important events in the family, and at regular times sacrifices of food were offered to them. Thus the dead continued to take part in the activities of the living, the unity of the family traversing the barrier between life and death. These facts explain the background of Chapter 21 of this novel.
Ancestral worship supplies also one of the reasons why the desecration of a grave was legally a capital offense. The Chinese Penal Code which was in force till the establishment of the Republic in 1911 states in Section CCLXXVI: "All persons guilty of digging in, and breaking up another man's burying ground, until at length one of the coffins which had been deposited therein, is bare and becomes visible, shall be punished with 100 blows, and perpetual banishment to the distance of 3,000 miles. Any person who, after having been guilty as aforesaid, proceeds to open the coffin, and uncover the corpse laid therein, shall be punished with death by being strangled, after undergoing the usual confinement" (cf. Ta Tsing Leu Lee, the Penal Code of China, translated from the Chinese by Sir George Thomas Staunton, London, 1810).
As regards the personality of the boxing master Lan Tao-kuei, it should be noted that Chinese boxing is a very old art, aimed at promoting one's own physical and mental health rather than at vanquishing an opponent. In the seventeenth century Chinese refugees introduced this art into Japan, where it was developed into the famous Japanese art of self-defense, judo or jujitsu. As to the relation between Master Lan and Mrs. Loo I may remark that the ancient Chinese had certain theories which, if practiced in the left-handed way, resembled our medieval vampirism. Those interested will find more details in Dr. Joseph Needham's Science and Civilisation in China (Cambridge University Press, 1956), Vol. 2, page 146, where also my own publication on the subject is referred to.
The quarrel about the broken cakes and its solution used in Chapter 14 of the present novel is taken from the Tang-yin-pi-shih mentioned above, Case 35. There its solution is ascribed to Sun Pao, a perspicacious judge of the beginning of our era.
The Seven Board, in Chinese called Ch'i-chiao-pan, "Seven Clever Board," or also Chih-hui-pan, "Wisdom Board," is an old Chinese invention that was especially popular during the sixteenth and seventeenth centuries. Then some well-known scholars published books with series of figures that can be made with the board. In the beginning of this century it found its way also to Western countries, and is still occasionally seen in toy shops.