A man kills his unfaithful wife and gets two years. A woman kills her violent partner and gets life. Not fair, says Justice For Women, 10 years old tomorrow. Rachel Cooke reports

Josephine Smith shot her husband Brian in the head while he was asleep at home in King's Lynn, Norfolk. She later told Norwich crown court that his death on July 30 1992 followed a row in which he had interrogated her about what she had been doing during the day. The gun belonged to her father. She had stored it in the boot of her car because she was planning to leave her husband, taking her three children with her. Without it, she feared they would not be able to get away.

During her trial, the court heard that Smith had subjected his wife to years of physical and mental abuse. He monitored her car mileage and telephone calls; he forced her to carry out sexual acts depicted in pornographic videos found by police at their home; and he beat her - she hid her bruises beneath make-up and polo-neck sweaters.

She had tried to leave him before, but he threatened to track her down and kill the children rather than allow her to go. Three psychiatrists gave evidence on her behalf. In spite of this, Smith's guilty plea to manslaughter on the grounds of diminished responsibility was rejected by the jury and in November 1993 she was convicted of murder. Since then, she has twice been refused leave to appeal against her conviction.

Her case is currently with the criminal cases review commission, the independent body which deals with alleged miscarriages of justice. Her supporters hope the commission will refer her case to the court of appeal on the grounds that the jury was prevented from knowing the extent of the cumulative provocation involved.

Smith's case is one of several being fought by London Justice for Women, the feminist group that began life as the Free Sara Thornton campaign, which celebrates its 10th birthday tomorrow. Over the past decade, JFW has had some stunning successes. In 1991, it organised a demonstration calling for the release of Thornton, Kiranjit Ahluwalia and Amelia Rossiter - all of whom had been jailed for life for killing their violent partners.

Within five years, the murder convictions of all three women had been overturned. In 1995, the court of appeal also freed Emma Humphreys, convicted of murder at the age of 17 for killing her abuser. The group's founders, Julie Bindel and Harriet Wistrich, also achieved a change in the law of provocation as a defence for murder. Until the mid-90s, 'sudden, temporary loss of control' had to be proved if provocation was to be used as a defence. JFW argued that this was inappropriate in cases involving domestic violence. "Now there can be a gap between the final act committed by the abusive partner and the homicide," says Bindel. "The idea of cumulative provocation is widely understood. Rather than cooling down when her partner goes to sleep, she boils over. A dam bursts. She can't take any more. Next thing she knows, she has a knife in her hand."

So why, then, are Josephine Smith and others like her still serving life sentences? "It's terribly depressing," says Wistrich, a solicitor. "In the last year, I've found myself dealing with four new cases in which women have been convicted of murder when clearly the issues of domestic violence, provocation and self-defence are all there."

Between 12 and 15 women kill their abusers every year - compared to 100 men who kill their partners. Worse, violent men who kill are still getting away with using what Bindel likes to call the 'nagging and shagging' defence. In February 1994, two months after Smith was convicted, Roy Greech was given a two-year suspended sentence for killing his wife because she was having an affair.

In 1997, David Hampson got six years for manslaughter after beating his wife to death with a hammer because she nagged him; his sentence was reduced to four years on appeal. "The judiciary and the jury understand what causes a man who has been habitually nagged to kill," says Bindel, a researcher at the University of North London. "They are less able to deal with thinking about being raped and battered. It is not our aim to pass a law that means a woman who kills her partner doesn't have to answer her charges - of course she should be tried in a court of law. It's about re-educating people so they understand why the crime was committed." JFW is funded solely through donations.

"We don't say yes to everyone," says Bindel. "We tend to take on only the very hardest cases because we want them to have as wide an impact as possible." The group gathers expert witnesses, lobbies MPs, organises fundraising events and public meetings and, crucially, tries to keep the women's morale high. Its solicitors spend a lot of time visiting women in prison, trying to build up as full a picture as possible of the abuse.

Diana Butler was convicted of the murder of her violent partner, Roger Carlin, in December 1997 after she stabbed him at their home in Doncaster. Her conviction was quashed on appeal the following year. During the retrial, the prosecution accepted her plea of guilty to manslaughter. "I couldn't have got through my second trial without [JFW]," says Butler. "I could speak freely about what had happened to me without them being shocked or disgusted, and they didn't think I had made the whole thing up just because I didn't speak about it at my first trial. In the beginning, I thought I deserved to be locked up forever. I'm not justifying what I did, but they made me see I had been driven to commit a crime."

Meanwhile, the fight to overturn Smith's conviction and those of others goes on. JFW is particularly concerned about the cases of Joanne Cole and Christine Devaney, both of whom received life sentences earlier this year. The group has also taken up the case of Jane Andrews, former dresser to the Duchess of York, who was convicted of the murder of her partner Thomas Cressman in May. An appeal has been lodged.

Justice for Women will celebrate its 10th birthday tomorrow evening when the annual Emma Humpreys memorial prize will be awarded. JFW set up the prize, now in its fourth year, to commemorate the life of Humphreys, who died of an accidental overdose of the medication she became addicted to in prison in 1998. The prize is awarded to a woman or group who has raised awareness of violence against women and children. This year, it will go to Anne Ward who killed a man who raped a close member of her family.

Since her trial - the jury refused to convict - she has worked as a campaign officer at her local women's centre."I can't believe they have picked me," she says. "They deserve the medal. They have no thought for themselves. Their kindness is overwhelming."