In almost every culture and every period of history, a she-devil emerges as an example of all that is rotten in the female sex. This Medusa draws together the many forms of female perversion: a woman whose sexuality is debauched and foul, pornographic and possibly bisexual; a woman who knows none of the fine and noble instincts when it comes to men and children; a woman who lies and deceives, manipulates and corrupts. A woman who is clever and powerful. This is a woman who is far deadlier than any male, in fact not a woman at all.

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The perversion of the human spirit that underlies crimes of desperate cruelty invokes an atavistic desire to punish till the end of time those who inflict such pain on their victims, and on the scarred families who are left to mourn. It is tempting to characterise all women criminals as victims, because so many of those who go through the system have themselves been on the receiving end of criminal behaviour. There has been a tendency, in fighting the women’s corner, for feminists to go into denial about women’s capacity for cruelty and wickedness. But there are women who commit crimes as terrible as any committed by men. They just happen to be the outliers.

Men enter the pantheon of monsters more often than women; but convicted killers who do not belong to the dominant culture are more likely to be mythologised. The imprisonment of Myra Hindley came to stand for more than simple punishment for an abhorrent crime; her long incarceration symbolised our fear of returning to a more primitive past. In an increasingly secular world, a woman like Hindley is the vessel into which society pours its dark secrets; like a war criminal, such a “she-devil” is a reminder of what is horribly possible.

Hindley was and remains the embodiment of all that is unnatural in women. Yet, if you ask people under 50 what she actually did, they are uncertain, apart from a hazy appreciation that children were killed and that the case had sadistic, sexual overtones.

It is impossible to fathom what corruption or disturbance of the human spirit can account for the horrible crimes Ian Brady and Hindley committed, and no lawyer is going to be able to provide the answers.

The investigation began in October 1965 when David Smith, Hindley’s brother-in-law, informed Manchester police that he had been witness to the savage murder by Brady of a 17-year-old youth. Police went immediately to the Brady and Hindley’s address and found the boy’s dead body cleaved by an axe.

A notebook discovered in the house contained a list of names, including that of John Kilbride, a 12-year-old boy who had gone missing two years earlier. The police sensed they might be dealing with a complex investigation. They scoured the property for information on Kilbride’s whereabouts, and found photographs taken on the nearby moors. A search of Saddleworth Moor unearthed the body of another child, Lesley Ann Downey, who had disappeared the previous year.

The case began to come together when Smith also recalled that he had seen Brady remove two suitcases from the house. They were discovered in the left-luggage office at the city’s central station and contained crucial evidence linking the pair to the little girl. Days later, Kilbride’s body was also found on the moors.

Facebook Twitter Pinterest Myra Hindley circa 1965. Photograph: National Archives/PA

The contents of the cases included books on sexual perversion, coshes, photographs of Downey naked and a tape recording of her screams. The voices of Brady and Hindley are clearly audible, remonstrating with the little girl, telling her to shut up and to cooperate. The child is threatened and told to put something in her mouth. The playing of that tape in court did more than any other piece of evidence to secure the convictions.

At their trial in Chester in 1965, Hindley was presented by the prosecution, and by Brady, as his faithful lieutenant. The press described her as his sex slave, and there was little doubt at the time that, while her role was criminal and appalling, she was not the prime mover in the murders. The trial judge, Mr Justice Fenton Atkinson, suggested she might be capable of reform. He said: “Though I believe that Brady is wicked beyond belief without hope of redemption, I cannot feel the same is necessarily true of Hindley once she is removed from his influence.” But as the years passed, she moved centre-stage. Brady’s psychosis became well established, and he served his sentence in a penal institution for the insane until his death in 2016. The mad dog was safely caged; whatever power he had once wielded, he became, we are told, a pathetic, demented specimen.

Not so Hindley, whose survival and persistence in seeking parole right up to her death in November 2002 was seen as a testament against her. I acted for her in 1974 when she pleaded guilty to plotting with a prison warder to escape. The warder was a former nun called Pat Cairns, who had fallen in love with Hindley. Their affair, which lasted three years, created a media feeding frenzy of prurience about lesbianism. Newspapers paid former inmates for stories about alleged sexual trysts in the chapel at Holloway prison. Here, they inferred, was further proof of deviance.

In 1994, Hindley published a statement, begging for forgiveness: “After 30 years in prison, I think I have paid my debt to society and atoned for my crimes. I ask people to judge me as I am now, and not as I was then.”

She claimed in 1998 that she had been abused by Brady, who had threatened to kill her sister, mother and grandmother if she did not participate in the killings. She applied again and again for parole, but successive home secretaries refused, knowing that the public would be outraged. She remained in prison even while she was dying of cancer.

Dreadful crimes challenge our beliefs in fundamental goodness, and if there is no understandable motive, such as jealousy or greed or a response to some form of provocation, we cannot comprehend them.

We are disturbed at our failure to categorise such conduct beyond accepting that it falls well outside the bounds of moral acceptability. We are happier cataloguing it as a result of madness, because we do not then have to deal with the troubling concept of wickedness. Madness, for all its elusiveness, is a label that gives us comfort in the face of inexplicable behaviour. Yet there is ambivalence about how it is used. The public want murderers convicted as murderers rather than madmen if they have killed in cruel and vicious ways; they want lunacy to be diagnosed after the magnitude of the crimes is recognised, not before. The catharsis of public condemnation has to be ritually experienced.

There is a conflict between seeking an explanation for the inexplicable in madness and an unwillingness to allow madness to become an excuse. When we ask ourselves, “how could someone do that to another human being, to an innocent child?”, we want someone to make the behaviour intelligible to us.

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Explanations for deliberate acts of criminality are sometimes not available; although these occasions are comparatively rare, there are motiveless crimes with no suggestion of any diagnosed disease of the mind. And, of course, if they are denied by those charged with their commission, no insight comes from the offender.

Evil as a concept is resisted by some, but the majority do accept it, and want punishment for its perpetrators. Sexual depravity as a component in killing heightens our revulsion, and our inability to understand becomes more pressing if children are involved.

We feel differently about a woman doing something consciously cruel because of our expectations of women as the nurturing sex. The adage is that women who commit crime are mad, bad or sad. The bad may be few in number, but once given the label there is no forgiving. It defies explanation that someone, especially a woman, stood by and allowed torture to take place, but it is important to remember that women did it in the concentration camps, and evidence is emerging that women are doing it in Syria and Iraq with Islamic State. Terror is a man, but wickedness is a woman.

In 1986, the moors murders case was reopened when Brady was said to have confessed to reporters that he had also killed two other young people, Keith Bennett and Pauline Reade. In the prison interviews with the police that followed, Brady refused to help, but Hindley admitted they had been murdered. She described the unbearable pain of confessing to crimes of such enormity, but wanted the whole thing to be laid to rest for herself and for the families.

The lucid explanation that Hindley put forward to explain (but not excuse) her involvement in the killings – that she was then a naive young girl totally in thrall to a complex, experienced man – missed its mark because of the very coherence with which it was expressed.

It was hard to see beyond the strength of character and force of will that she came to exude in middle age. Her all-too-late confessions of guilt in relation to the original charges and the further admissions of two additional murders were hard to interpret as genuine repentance, and appeared rather as part of calculated machinations for getting herself released. Press revelations of her lesbian relationships in prison, in an era of deeply ingrained hostility to anyone who was gay, never mind a convicted felon, had further stoked the fires of abhorrence.

There are very few female serial killers, by which I mean people who successively murder strangers. When the nurse Beverley Allitt stood trial in 1993 for the killing of babies and young children, the public were horrified. She was diagnosed as suffering from Munchausen’s syndrome by proxy, in which women use the ostensibly caring role of mother, nurse or nanny to inflict harm on children. While she was clearly shown to be highly disturbed and dangerous, the degree to which her offences were treated with disbelief and then moral panic reflected the extent to which she, as a nurse caring for children, had shattered the image of womanhood held most sacred by the general public.

On the few occasions when women have played a role in serial killings, as in the moors and Manson murders, they have functioned as handmaidens to a master. This is not the same dynamic as the battered wife who submits or colludes because of her own passivity in the face of violence. These are women in the power of strong-willed men who kill to express their scorn for humanity, men who see themselves as superior and are empowered by exacting the ultimate price from their victims. Some women feel perversely flattered at being chosen by such men, as though they had been singled out from the ordinary run of womankind.

Facebook Twitter Pinterest Maxine Carr. Photograph: PA

There are people whose sexual makeup seems to require a relinquishing of personal will; it implies never having to face moral responsibility for sexual indiscretion or having to accept guilt if your deviance becomes criminal. It may be that at that time in her life Hindley needed Brady’s sexual control just as much as he needed a witness to his atrocities, and that they then became welded together by their mutual knowledge. No one should be surprised at Hindley’s reconstructing of the past. We all do it, and the enormity of her shame must require some delusion. But every attempt she made to explain her acts only fed the idea of her as a devious, manipulative woman. Her own gender is especially repulsed by her crimes.

Women who murder summon up a special revulsion, especially if they do not present in a sympathetic way. Hindley did not cry. Real women cry. Yet, even when they do, it can be met with scepticism. When Ian Huntley stood trial in 2003 for the murder of Holly Wells and Jessica Chapman, two 10-year-old girls, his girlfriend, Maxine Carr, was also in the dock, charged with providing him with a false alibi. Carr’s account to the police was that she was upstairs in the bath when the little girls came to the house asking for her. She claimed that she heard Huntley speak to them outside, but that they then left without anything untoward happening. She was in fact 100 miles away in Grimsby. In the week before being arrested, she helped Huntley clean the house from top to bottom, which might have destroyed potential forensic evidence.

At her trial, Carr admitted lying, but described her relationship with Huntley as one in which he was controlling, jealous and at times violent. She said that she had provided an alibi for Huntley at his insistence because he had been falsely accused of rape in the past and said he might face the finger of unjust blame again because of that history. She said she could not let herself believe that he had killed the girls.

However, DCI Andy Hebb, the second-in-command on the inquiry team, was unimpressed by Carr’s tearful performance in the witness box, and remained convinced that she must have had her suspicions about what Huntley had done. “Rather cynically is how I view it,” he told the Observer in December 2003. His view, so publicly expressed, fed into the general vilification of Carr in the press. Public vitriol was such that she had to be given a fresh identity and placed in a safe house on her release from prison.

Another case that created a new she-devil in criminal iconography was that of Amanda Knox, who was initially convicted of murdering Meredith Kercher in Perugia, Italy, in November 2007. Ultimately she had her conviction definitively quashed in 2015 by the Italian supreme court of cassation, but not before every detail of her sex life had been minutely examined and laid before the public via the internet and the tabloids.

Kercher, a British student at Leeds University, was undertaking a year of study abroad as part of her degree. She was brutally murdered. Her throat was cut with such ferocity that her head was almost severed. She was found semi-naked in her bed in a house she shared with Knox.

Knox, an American, and her Italian boyfriend, Raffaele Sollecito, were interrogated and eventually charged with the murder. A man called Rudy Guede was also charged with murder and was tried separately.

However, it was Knox who captured the salacious fascination of the media when her diary was leaked from the prison to a journalist and her sex life was revealed in lurid detail. She said she had recorded her relationships because she was wrongly informed by the Italian prison authorities that she was HIV-positive and she was cataloguing those with whom she had had sex. The Italian prosecutor claimed that Knox’s motive for killing her housemate was Knox’s “lack of morality”. She was filled with a desire “for pleasure at any cost” and marks on Kercher showed the knife had been wielded “teasingly” with the point piercing the neck before being plunged into the young woman.

Guede was convicted of murdering Kercher, and of sexually assaulting her. Guede was a known burglar and his bloodstained fingerprints were found on Kercher’s possessions.

When Knox was filmed after her eventual reprieve, she spoke about how she came to be perceived. “I was some heinous whore – bestial, sex-obsessed and unnatural.” She pointed out that she had had sex with seven men – not a world record. There is no doubt that her sexual desire as a young woman was used to implicate her in the murder. She was asked on primetime television whether she was into deviant sex. Throughout the case, judgments about Knox were being based on how we perceive female sexuality and what it says about a woman if she has multiple lovers. It is these extraneous factors that make justice processes for women so much more fraught with risk.

In her authoritative book Women Who Kill, Ann Jones suggests that moral panics about women and crime coincide with periods when women make strides towards equality, and that such panics may be a crude and perhaps even unconscious attempt at controlling these advances.

The trial of Ruth Ellis – the last woman to be hanged in England, after being found guilty of murdering her lover – took place in 1955, when women were being shooed back into domesticity after the war. But where Jones’s theory has most potency is in the legal response to women who are involved in political crusades, or are fighting for equality. The women who have most seriously confronted the male authority of the court are those whose offences emanate from their political beliefs.

The 1970s and 80s saw many politically active women coming before the courts, due to their involvement in anti-nuclear campaigns such as the women’s peace camp at Greenham Common, or feminist demonstrations such as Reclaim the Night and Women’s Right to Choose on abortion. These public campaigns echoed the suffragette campaigns of the beginning of the century. The response of the court had changed remarkably little, and many of these women voiced criticisms of the patronising and paternalistic nature of the system very similar to those of the suffragettes.

The operation of the criminal justice system in public-order cases always produces feelings of anger. The mass processing involved in dealing with multiple cases arising out of the exercise of political freedom inevitably creates a sense of injustice. In most circumstances, the response of the court is no different whether you are male or female, but some other component does come into operation when the demonstration is actively organised by women for women.

In the early days of the Greenham trials in Newbury, the celebratory atmosphere of women coming together demanding peace penetrated the courtroom. The magistrates were perplexed and unsettled by the motley collection of women appearing before them: women of all classes, ages and marital status, gay women, nuns, mothers. I was instructed to represent a group of these women in court. After making a legal argument about the right of way and not succeeding, we agreed that I would withdraw so the women could make their own political statements. I stayed to watch, and it was quite extraordinary to see how the traditional regimented courtroom procedure was changed. One after another, the women gave forceful explanations of why they were involved.

Their large numbers together in the dock meant they were not intimidated, and could express themselves freely in what is normally an inhibiting male theatre. They gave each other encouragement and support.

However, this female insurrection had to be contained, and a decision was made to separate the women so that only one or two were tried at once. The diversity of the women involved was soon homogenised by the press into the 1970s stereotype of dungarees, spiked hair, non-matching earrings and no trace of lipstick. The legend was created that this or that woman was a man-hater, an iconoclast with no respect for institutions, a woman who abandoned her responsibilities of home, hearth and children to haunt the perimeters of legitimate male activity in defending the realm. The antagonism towards the Greenham women was soon tangible in the courtrooms; in the most minimal of obstruction cases, questions would be asked about whether the women had children, and who had been caring for them at the time of their arrest. No miner on a picket line would ever be asked to account for himself in this way.

Facebook Twitter Pinterest A peace protest in 1982 at Greenham Common air base. Photograph: PA

Greenham went from being portrayed in the press as a legitimate peace campaign to a sideshow, and eventually a freakshow. This process of marginalisation was completed in the courts. But contemporary politics has thrown up a different kind of political she-devil. The terrorist woman is a different category of female offender, in that she challenges the pathos of so much female crime. Her attack upon the state is dual: assaulting its institutions directly, in bombing attacks; and indirectly, by confronting the traditional role of woman as a cornerstone of established society.

There seems to be a sexiness about the combination of young women and power; the words “cold”, “calculating” and “ruthless” are often juxtaposed with “attractive”, “vivacious” and “pretty”. In many of the cases of IRA activity involving women, male police officers, lawyers, judges and reporters were titillated by images of the Armalite rifle in feminine hands – but also fearful of its implications. Running through the cases is a sense of horror that women should use the very attributes that make them so appealing to men to undermine their guard.

There is a complicated relationship between sex and guilt, punishment and power. These elements charge the atmosphere at the trials of political, independent women, and, as a result, subtle and insidious inferences undermine the proceedings. There is no difference in the way women are sentenced – the courts cannot be criticised for inequality on that score – but the sense of alarm that they should be involved in such warlike activity infects the rhetoric of the courtroom.

The women striking terror into hearts today are those involved with Isis and other extreme Islamist groups. The most prominent is Samantha Lewthwaite, the daughter of a former soldier who was born and grew up in County Down, Northern Ireland, but came to London to study, and converted to Islam. She was the wife of Germaine Lindsay, who blew himself up on a Piccadilly line train between King’s Cross and Russell Square stations, one of the four suicide bombers who caused multiple explosions in London on 7 July 2005, killing 52 people and injuring more than 700 others.

Lewthwaite and her children experienced a revenge arson attack on their home when her identity as a terrorist’s wife became known. She disappeared soon after, and is believed to have gone to Somalia, and to have married the warlord Hassan Maalim Ibrahim, a senior figure in the terrorist group al-Shabaab. She became one of the most wanted women in the world, and in 2013 Interpol issued a red notice warrant for her arrest. She is said to have masterminded many terrorist attacks, including the bombing of a bar in Mombasa in Kenya in 2012, where tourists and locals were watching a football match. It is claimed she ordered the assassination of two Muslim clerics and two Protestant preachers. She was also linked to the bombing of the Westgate mall in Nairobi in 2013, and the massacre at Garissa University in 2015, in which 148 people were killed.

In September 2016, three female jihadists stormed a police station in Mombasa. One attacked a police officer with a knife and another threw a petrol bomb. All three were shot dead. One had with her an unexploded suicide vest. Laptops and emails belonging to the three women indicated they had been in communication with Lewthwaite. Security services claim she has been involved in grooming women online, encouraging many to leave their families and travel to places such as Syria and Somalia to participate in the creation of Islamic states. Al-Shabaab has been linked to al-Qaida and Boko Haram, but recent outrages in the region have been claimed by Isis. There is some speculation that Lewthwaite is now dead.

Another woman flagged on the most-wanted terrorist list until 2017 was Sally Jones, otherwise known as Umm Hussain al-Britani. She was a single mother of two living in Kent when, in 2013, she began communicating online with a young Muslim hacker called Junaid Hussain.

He drew her into Islam, and when he decided to go to Syria, he urged her to join him. That winter, she left the country with her nine-year-old son, Joe. Her older son, who was 18, chose to remain in the UK. She married Hussain the day she arrived in Syria, and converted to Islam. Joe’s name was changed to Hamza. They then travelled to Raqqa, where Hussain began military training, and Jones was inducted into Islam and Isis’s extreme interpretation of sharia law.

Facebook Twitter Pinterest Samantha Lewthwaite in a photograph released by Interpol

Soon after, Hussain took a young Syrian woman half Jones’s age as his second wife. Most of the fighters had more than one wife, but they usually took and enslaved Yazidi, Christian or Shia women. Jones boasted on social media of her wonderful life under the caliphate.

Intelligence reports claimed she recruited dozens of young women and, according to defectors who became informants, she quickly rose to a prominent position because of her success in encouraging followers to carry out attacks against the west. The substance of these claims is unknown.

Hussain was suspected of being behind Isis hacking attacks, and of recruiting sympathisers in the west to carry out lone-wolf attacks. It is also believed that he provided Isis with radar technology. As a result, he became a high-profile target for the US military, and in August 2015, he was killed in a drone strike in Raqqa.

Jones reportedly moved into a high-level training role as a jihadi widow. She is believed to have trained a special unit of female European recruits in the use of firearms and bombmaking, and showed them how to plan and execute suicide attacks. French intelligence linked her to the arrests of three women who were found with gas canisters and other material in Paris in 2016. Jones and her son were reported killed in another US drone strike last year.

Reports in May 2017 estimated that 50 British women had headed for Syria and Iraq in the preceding year, some travelling with husbands and even children, others travelling alone or with friends, drawn by a heady mix of romance, adventure and piety. Others believe these numbers are greatly underestimated. The call to women to come and help build a new Islamic state captured the imaginations of many jihadi brides. In February 2015, CCTV footage showed Amira Abase, Shamima Begum and Kadiza Sultana, three schoolgirls from Bethnal Green in east London, setting off for Syria via Istanbul. They remain missing, and there are fears that some or all of them might now be dead.

Undoubtedly, some of the women are as politically committed as the men, but very many were brainwashed into believing they were going to create an ideal Islamic state – perhaps including these three girls. They must have been psychologically scarred by what they found awaiting them in Syria, and might have had second thoughts, but by then had no way out.

Within Isis, women are commonly bought, sold or traded. They are used as tools to retain disillusioned troops, made to police the women in local populations, forced to produce children and made to accept their place as one of several wives. Yazidi women in refugee camps and in asylum refuges in Germany reported watching their fathers and brothers massacred and then being multiply raped by their captors. They also recount being ill treated by Isis women.

As Isis has been slowly beaten back, many of its women are now being held in prison camps in the parts of Syria controlled by Syrian Kurds. UK government ministers would prefer that fighters who left Britain to join Isis never return, or that they are prosecuted for war crimes and terrorist activities in the countries where they were captured. But there can be little confidence of fair trials in countries such as Syria and Iraq.

There is unlikely to be much sympathy for jihadist women who return to the UK, but the system ought to rise above visceral, emotional responses. Travelling to join a terrorist organisation is a crime in and of itself. Some girls were stopped by the authorities at airports before leaving the country, and careful decisions were made as to whether prosecution was necessary; often it was not. But when women return and there is evidence of complicity in terror, recruitment, cruelty to enslaved women or other criminal actions, they will face trial, and if convicted, will rightly receive long prison sentences.

Nevertheless, my experience of seeing the human cost when legal standards are lowered and wrongful convictions follow has taught me the imperative of keeping the bar high. The profound misogyny of Isis means that some of these women will themselves have been victims of terrible abuse, and will have been subjected to duress and coercion. The legal system will have the difficult role of charting a course through uncorroborated accounts, fragile evidence and strong public hostility to determine where real guilt lies. This is the complex terrain of justice, and it requires our utmost vigilance.

This is an edited extract from Eve Was Shamed: How British Justice Is Failing Women by Helena Kennedy, published by Chatto & Windus on 11 October and available at guardianbookshop.com

• This article was amended on 2 October 2018. Because of an editing error, an earlier version stated that Ruth Ellis was convicted of murdering her husband, rather than her lover.

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