Is Battered Woman Syndrome recognized by the law as a legal defense?
That's a great question.
The case here in the UK seems to be that while the diagnosis is not used as a legal defense - generally 'provocation' is seen especially in the early nineties when these sorts of issues were arising.
From a historical perspective, perhaps it is not so surprising that the law has such a hard time defining the answers to these questions - as it has taken so long for 50% of the population to achieve a semi-equality. Social changes have now informed public policy to some extent and civilisation has realised that spouses don't have ultimate control over women and that violence is unacceptable no matter the relationship.
In my own opinion: This is a question of saving oneself, women in abusive relationships often feel trapped and feel as if there is no way out. So the law needs to take intou account the coercive nature of control that so often prepares the ground for these murders to take place.