Many of those researching their family tree will have discovered an ancestor who has gone through a ceremony of marriage with more than one person, without any intervening death or divorce to free them from their first spouse. But what risk were they running in doing so? And what might the sentence handed down in any particular case tell us about an ancestor’s life? Drawing on the 2,500 or so cases heard at the Old Bailey between the early 17th century and 1913, together with thousands of newspaper reports of provincial cases, it is possible to offer insights into exactly which factors might have affected the sentence in any given case.

Before 1604, bigamy was dealt with by the ecclesiastical courts. Those who remarried during the lifetime of their first spouse faced excommunication – a form of spiritual death. In 1604, however, Parliament made bigamy a felony that was punishable by actual death, and throughout the 17th century both men and women were put to death for the offence.

But the last occasion that this sentence was handed down at the Old Bailey was in 1693. For the next few decades, the only punishment meted out there for bigamy was that of branding, with the convicted bigamist being burnt in the hand. From the 1750s, this was often commuted into a fine – usually just one shilling – although almost invariably accompanied by a period of imprisonment.

Then, in 1795, legislation was passed allowing individuals to be transported for the offence. It is at this point that we see the courts beginning to develop a more nuanced approach to the crime, reflecting the broad range of punishments available. By the 1810s transportation had become the most common punishment for bigamy: over half of those found guilty received this sentence. These were not generally cases of aggravated bigamy, simply ones in which there were no clear mitigating factors. The cases ranged from a man who claimed that the separation from his first wife had been consensual and that she had proposed that he sell her at Smithfield market, to a husband whose first wife had clearly not consented to any separation, and who turned up to claim him back three hours after the second marriage had taken place.

However, this soon changed. As early as the 1820s the use of transportation had begun to decline, and by the 1840s it was clearly only being ordered in the worst cases. Of the 21 men sentenced to transportation at the Old Bailey in that decade, seven were guilty of more than one bigamous marriage, six had married for financial gain, three had deceived their second spouses by using an alias, and two had already left the second spouse. The particularly egregious case of Henry Bramell – alias Beaumont – involved all four aggravating factors, leading to him receiving a double sentence.

After 1853 no Old Bailey bigamists received a sentence of transportation. So when legislation in 1861 substituted a period of seven years’ penal servitude as the maximum sentence, it was merely recognizing that practice had already changed. And most received much lesser sentences: the maximum sentence of seven years was only imposed in a handful of cases, almost invariably ones involving additional marriages or obtaining money by false pretences.

By the final decade of the 19th century the most common sentence handed down was the virtually nominal one of imprisonment for a week or less, reflecting the fact that there were often mitigating circumstances. So what factors were regarded as reducing or removing the harm of bigamy?

The gender of the offending spouse made a big difference. Women, who always constituted a minority of those accused of bigamy, were far more likely to be acquitted than were men, and the sentences handed down to female bigamists tended to be far lighter than those accorded to their male counterparts. From the 1790s to the 1850s only one woman was sentenced to transportation at the Old Bailey, while in the second half of the 19th century no woman received a prison sentence of more than a year, and only four received more than six months. Most women accused of bigamy were either acquitted or given a sentence of fewer than seven days. Those who had been the victim of violence at the hands of their first husband were particularly leniently treated: of the four women alleging violence in the 1890s, two were found not guilty, despite proof of the two marriages, while the other two received sentences of four days and one day respectively.

A second factor that would affect the sentence was whether the second spouse was aware of the former marriage. The courts took the view that no harm had been done to a woman who freely consented to enter into a marriage that she knew was void. Similar reasoning meant that any evidence of pre-marital cohabitation before the second marriage would also mitigate the sentence, the court taking the view that a woman who was willing to live with someone without marrying them was not harmed by the fact that the subsequent marriage turned out to be void. (Men, it was thought, did not suffer as much from the invalidity of the second marriage even if they were not aware of the facts.)

Finally, it should be noted that the mere fact that someone has gone through two ceremonies of marriage does not necessarily mean that they are guilty of bigamy. The statute had always provided a defence in the case of seven years’ absence, and in 1856 it was held that the lack of evidence that the prisoner knew the first spouse was living during that time had to be taken as a finding that she did not know. In 1889 it was held that someone who reasonably believed the first spouse to be dead, and remarried within the seven-year period, lacked the intention to commit bigamy and would be acquitted.

Some of those tracing their bigamous ancestors may be lucky enough to find a record of the prosecution and trial, which will often give information about the two marriages, as well as details of age, occupation and even address. Newspaper reports of the committal stage in front of magistrates often offer a particularly rich seam of information, since at the later assizes bigamists often pleaded guilty. But whether you have discovered such records or simply suspect that an ancestor may have committed bigamy, knowing what sentences were handed down in different cases provides context against which any findings can be interpreted.