The Chris Huhne / Vicky Pryce driving trial has brought to the fore a defence many didn't even realise existed, namely that of marital coercion.
Marital coercion arose from the old common law rebuttable presumption that save for the most grave crimes (treason, murder), a wife could not commit a crime whilst in the presence of her husband as she was automatically assumed to have been coerced.
Perhaps surprisingly , the defence was given a statutory basis as late as 1925 with the passing of s47 of the Criminal Justice Act 1925. S47 states: “Any presumption of law that an offence committed by a wife in the presence of her husband is committed under the coercion of the husband is hereby abolished, but on a charge against a wife for any offence other than treason or murder it shall be a good defence to prove that the offence was committed in the presence of, and under the coercion of, the husband”
A defendant relying on this defence therefore has to prove two things, on the balance of probabilities:
- That the crime was committed in the presence of her husband
- That the crime was committed under the coercion of her husband
The case of R v Ditta, Hussain and Kara  Crim LR 42 CAmakes it clear that interpretations of s47 are strict, with little to no scope for widening the ambit of defence. The defence is therefore only open to married women and excludes husbands, civil partners and common law wives. (The status of wives in polygamous marriages legally conducted in other jurisdictions is unresolved).
In R v Cairns  1 WLR 796 the Court considered the issue of marital coercion in the context of the defence of duress and stated “It is clear that coercion must be given a broader meaning than duress because otherwise this statutory defence would serve no useful purpose and add nothing, especially since it requires proof of the additional ingredient of the presence of the husband”
The leading case on what coercion actually means is that of R v Shortland  1 Cr App R 116. In that case, the judgment makes it clear that the wife need not necessarily demonstrate the threat or use of force against her but that merely loyalty by her towards her husband will not be sufficient. In essence, what the wife must prove is that her will was “overborne by the wishes of her husband”
In 1977, the Law Commission considered the defence of marital coercion and recommended its abolition (Law Com. No. 83) but this recommendation was not acted upon leaving the defence still open today.