Joan Smith: A crime to take the breath away. When a father becomes a killer

When a father was dragged alive earlier this month from a house fire in which his wife and four daughters perished, my first thought was that the family, who were Asian, had been the victims of a racist attack. It didn't take long, however, for Lancashire police to announce that the fire had been started inside the house and they weren't looking for anyone else in connection with the incident. When Mohammed Riaz died in hospital two days later, detectives closed the book on another dreadful case in which a man had wiped out most of his immediate family.

Last week, another family was found slaughtered, this time in Newcastle. The bodies of Olufunke Sobo, 36, and her brother, Yemi, were discovered downstairs, while her son and daughter, aged five and 12, were found lying upstairs.

These terrible events are the latest in a catalogue of killings: in the case of Riaz it was carried out by a man whose response to the breakdown of a marriage was extreme violence. Friends of the family said that the couple's marriage was in trouble and Riaz feared that his wife, Caneze, who was 10 years younger, intended to leave him. It's clear that some thought went into his arson attack; the fire service confirmed that accelerants were used.

The idea that anyone could cold-bloodedly contemplate killing his wife and children takes the breath away. There has been speculation that the Riaz case was an "honour" killing, but it isn't just men from ethnic minorities who behave like this. In another recent incident, on the island of Crete in August, a man called John Hogan jumped from a hotel balcony with his two young children after rowing with his wife; his daughter survived but his son died from his injuries.

Whatever you choose to call it, such behaviour is an expression of patriarchal values at their most literal and deadly, a man responding to an affront to his authority by assuming god-like powers of life and death. It suggests two things: that his sense of masculinity is so fragile that he cannot tolerate rejection, and that he chooses not to exercise self-control over his destructive tendencies. These crimes are often not carried out on impulse; Gavin Hall was jailed for life for murdering his three-year-old daughter, Millie, after discovering sexually-explicit emails sent by his wife to another man. Hall repeatedly asked the child whether she wanted to "come with daddy" before smothering her with chloroform.

While the vast majority of men don't behave in this way, there's an urgent need to identify those who might - and educate boys so they don't become violently possessive partners. What would help is a clearer understanding of the characteristics of domestic violence, for while murders of this kind seem to come out of the blue, it's rare for them not to be preceded by emotional and physical abuse.

It's still too easy for outsiders to miss these warning signs, interpreting them as evidence that a man loves the partner he's abusing, or asking why the woman doesn't leave if the relationship is that bad. The truth is that women do leave abusive partners, and that's when they and their children are most at risk.

Women and their families need to know this, and get help from the police. It's also clear that from an early age boys should be taught self-control and how to handle hostile feelings, which might go some way to reducing crimes of violence generally. But the toughest challenge is getting abusive men to accept that their wives and children are human beings in their own right, not just extensions of themselves.