The former wife of ex-cabinet minister Chris Huhne has been found guilty of perverting the course of justice by taking speeding points on his behalf, in a case that brought a rarely used defence into the spotlight.
Marital coercion - which was used by Huhne's wife Vicky Pryce - is an old defence with an interesting history rooted, many believe, in a chauvinist past.
In modern times the defence has been used on just a handful of occasions, most notably by Anne Darwin, the wife of the canoeist John Darwin who faked his own death in order that the couple could claim life insurance and pension money and start a new life in Panama.
The defence was not successful in that case, and Anne Darwin was convicted in July 2008 for her part in the fraud.
However, it succeeded in the 2000 case of Ashley Fitton, who escaped a a drinking and driving offence after telling a court her irate husband had ordered her to get behind the wheel following a boozy meal at a restaurant.
She told the court she had refused repeatedly but had been scared of what her husband would have done if she had continued to refuse to drive. When stopped by the police she was three times over the limit.
It used to be the case in English common law that if a wife committed an offence (other than murder or treason) in the presence of her husband, she was presumed to have been coerced by him into doing it, and so she should be acquitted.
The presumption was abolished by Section 47 of the Criminal Justice Act of 1925, but in its place the defence of marital coercion was established.
It too applies to all offences bar murder or treason.
For it to operate two things have to be proved by the wife.
Firstly that the offence was committed in the presence of her husband, and secondly that it was committed under his coercion.
It is for the wife to prove these things to the civil standard, the balance of probabilities - in other words to prove that is it more likely than not the two things happened.
The burden is then on the prosecution to prove beyond a reasonable doubt that either the husband was not present at the time the offence was committed, or that he failed to coerce her into committing the offence.
But there is much debate and not a lot of case law on what amounts to coercion.
Marital coercion has something in common with the defence of duress.
However, that defence would require any threats made by the husband to be threats to kill or cause serious injury.
Marital coercion is therefore a broader defence than duress in that it is enough that the wife acted because of the dominating will of her husband, her own will being overpowered by his so that she had no choice but to unwillingly take part in the offence.
That is the really critical element. The jury will be asked to consider if the wife's will had been so overpowered that she had been impelled to commit the offence because she had truly believed she had had no real choice in the matter.
Some see the defence of marital coercion as a legal hangover from a bygone era.
In 1977 the Law Commission the body that keeps the law in England and Wales under review, recommended its abolition.
Many feel that it is absurd to have a defence that is only available to women, and then only to women who are married.
The defence is not available to women who are co-habiting with a man.
It is not available to husbands, and it was not extended to those in civil partnerships. Some feel it is no longer relevant in a world where many women are financially independent of their husbands and so less susceptible to coercion.
But there are others who feel that the unique relationship of marriage and the pressures it can impose on a wife, justify the retention of the defence of marital coercion.