Theodore Johnson first killed a woman in 1981. He tipped his wife Yvonne over the balcony of their ninth-floor flat in Blakenhall Gardens, Wolverhampton, having already hit her with a vase. Well, they had been arguing – a factor that enabled him to plead guilty to manslaughter on the grounds of provocation. The second woman Johnson killed was Yvonne Bennett, in 1992. He strangled her with a belt while their baby slept. Her “provocation” was that she refused the box of chocolates he had bought to win her back; he was able to plead diminished responsibility and, after a two-year stay in a secure psychiatric unit, was released and again free to form new relationships. Then, in December 2016, Angela Best became the third victim of Johnson, 64, and on Friday he will be sentenced for her murder. Best’s spur to his violence had simply been to end their relationship and start a new one with someone else.

Johnson’s case seems extraordinary. How could it happen? A list of victims, a history of violent and controlling behaviour in relationships … yet twice he was freed to kill again. Somehow, Johnson slipped through the system. Or was the problem that the system failed to take proper account of Johnson, of his capacity to kill, and as a result failed to take care of the women he went on to meet?

For all the apparent uniqueness of Johnson’s triple killing, he is not the only male perpetrator of femicide to have been given the opportunity to reoffend. In July last year, Robert Trigg, 52, from Worthing, was convicted of the murder of his partner Susan Nicholson six years earlier, and the manslaughter of his previous girlfriend, Caroline Devlin, five years before that. The deaths had initially been treated by West Sussex police as unsuspicious; the convictions were obtained only after the family of Nicholson, unconvinced by the police investigation, commissioned an independent pathologist.

And before that, in 1983, Keith Ward killed his partner, Julie Stead. He pleaded provocation, received a three-year custodial sentence and seven years later killed his ex-partner Valerie Middleton. According to the Office for National Statistics, one woman in four experiences domestic violence in her lifetime, and two women are killed each week in England and Wales by a current or former partner. So what does the case of Theodore Johnson tell us about the sentencing and treatment of domestic violence in the UK?

Theodore Johnson/ Photograph: Metropolitan Police/PA

Prof David Wilson is a criminologist with a special interest in serial killers. “When I looked at Theodore Johnson,” he says, “I saw a man who has killed three or more people in a period greater than 30 days. Technically, he’s a serial killer. What is the context in which he has been able to kill, especially after being incarcerated on two separate occasions? That context is misogyny. Women being killed by men who are in a relationship with them is seen as a thing that happens, something that just occurs. Last year, two women a week died at the hands of their partners or ex-partners. That is an extraordinary figure that begins to reveal something not about serial murder but about the phenomenon of everyday murder. There is this unreflective acceptance that violence towards women is normalised.”

Domestic homicide and domestic violence are better understood now than when Johnson was first convicted in 1981. But does there linger a sense that these are somehow explicable categories of homicide and violence? Maybe it’s that word “domestic” that seems somehow to qualify it. Media reports of such crimes tend to sympathise with the perpetrator. The Daily Mail, for instance, described Lance Hart, who killed his wife and daughter in July 2016, as “a jilted father” and quoted a source as saying: “I don’t know what the issues were in their marriage, but I can’t understand why he had to kill his daughter as well.”

An act of domestic violence tends to be seen as something that occurs within the walls of a particular relationship. It belongs to the relationship, rather than to society at large. “We often hear that the murder of a woman by a man is a tragic accident or a crime of passion – an isolated incident that surely will never be repeated,” says Katie Ghose, the chief executive of Women’s Aid and a former barrister. To shed light on the phenomenon of domestic homicide, Women’s Aid, in conjunction with Karen Ingala Smith (who set up the blog Counting Dead Women), has for the past two years published what it calls a “femicide census”. It records all the women killed by men in a year and last month published data for 2016 showing that 113 women were killed by men in England, Wales and Northern Ireland.

“The femicide census shows that these are not isolated incidents,” says Ghose. “They are part of a repeated pattern with misogyny as the root cause. I think that is probably what the case of Theodore Johnson is telling us: it is revealing a more systemic pattern and a failure in our society to wake up to femicide.” She uses the term “femicide”, she says, “to label very clearly the killing of women because they are women. But whatever the words, we need to get away from the idea that this is a family or private matter.

“What gets me,” she says, “is that these are repeated patterns of control and violence.” In the case of Johnson, he had a controlling relationship with all three of the women he killed. He twice attempted suicide after the killings; most recently he threw himself under a train after he murdered Best, and lost an arm and a hand in the process. These attempts, according to Wilson, are further examples of controlling behaviour. “It’s about him continuing to try to construct a narrative to explain what he did. He is trying to maintain control of the narrative.”

“It is the repeated patterns of behaviour that need to be exposed and which need to inform criminal justice,” Ghose says. She cites the most recent femicide census that found that more than two-thirds of women killed by men were killed by a current or former partner. Two-thirds of the women killed in 2013 were killed in their own home or the home they shared with the perpetrator; 77% of women killed by a former partner were killed in the first year after separation.

“If we better understood these patterns and root causes of fatal male violence against women, the criminal justice system can hand down more appropriate sentences for perpetrators who are high-risk,” Ghose says. “And when perpetrators are eligible for release, there should be proper support and protection for women. If the safety and the right of women to live freely were prized, we would not see patterns of male violence ignored.”

Domestic violence of all categories is not only a problem of the criminal justice system. After all, as Suzanne Jacob, the CEO of the charity SafeLives, points out, only one in five victims of domestic abuse contacts the police. When they do, and when a perpetrator is brought to justice, the most likely charges that will be brought against them are actual bodily harm or criminal damage, “neither of which carries a particularly robust sentence”. Women, on the other hand, who kill violent partners tend to be strongly sentenced, according to Harriet Wistrich, the founding director of the Centre for Women’s Justice: “Victims of domestic violence who retaliate are quite frequently convicted of murder, where men [who kill] are able to use defences to reduce their convictions.”

Some police forces have found creative approaches to confronting and curtailing domestic violence. Wilson mentions the case of Essex police, which removed guns from people with firearms licences who were suspected of domestic abuse, basing its confiscations on the testimony of victims and family members. Jacob at SafeLives recalls the case of Kylle Godfrey. In addition to his sentence for repeated violence against his partner, he was given a criminal behaviour order that requires him to inform police if he is in a relationship for more than 14 days. Police can then use Clare’s Law, the domestic violence disclosure scheme introduced in 2014, to inform that partner of Godfrey’s past. But there are limits to the effectiveness of the legal provision against domestic violence. The implementation of Clare’s Law, for instance, varies from force to force. Two years ago, coercive and controlling behaviour was made a criminal offence, but few cases have been brought under this legislation and just eight of 43 forces in England and Wales have provided training since its introduction. “It is still too rare to find police officers who understand the dynamic of domestic abuse and how to respond to it,” Jacob says. That someone might call the police for help, and then shut the door in their face, for instance, she says, should be understood as a response to controlling behaviour rather than a rejection of police help.

This year the government will introduce a domestic violence and abuse act, the specific proposals of which have yet to be announced, but which should help to clarify and unify the police response to domestic violence. The biggest change Jacob would like to see is better sharing of information. She reads a lot of domestic homicide reviews and many disclose that communication could have been better. Agencies such as police, probation, health services, housing, adult social care, child social care and substance abuse services “are holding back information from each other which, if shared, could save lives”.

At some point in the future, she will read the domestic homicide review for the case of Best’s murder by Johnson. What it won’t say is that the context of domestic violence still somehow persuades too many of us that such murders should be valued differently from a random killing by a homicidal stranger.

“It’s somehow seen as not as large a breach of the social contract we all have with each other,” says Liz Kelly, the director of the Child and Woman Abuse Studies Unit at London Metropolitan University. Nor is the review likely to mention misogyny, a word that is also absent from risk assessment forms. As Kelly says, “Misogyny is not seen as a form of extreme dangerousness … We need to identify these men who hate women and [understand] that they are a danger to all women.”