What does the Sally Challen case mean for women who kill their abusive husbands?

Sally Challen, who killed her husband in a hammer attack after saying she suffered decades of abuse has won an appeal to have her murder conviction quashed in a landmark ruling. She now faces a retrial. Jenni spoke to her lawyer, Harriet Wistrich, about the case and what it means for other women who kill their abusive husbands.