Joan Smith: So how many more women must die?

Once again the police are on the rack, bombarded with questions about the murder of a teenager who allegedly lived in fear of a stalker. This time the victim is a schoolgirl, Arsema Dawit, who was stabbed on Monday in the lift of the block of flats near Waterloo, south London, where she lived with her mother. The 15-year-old, whose family is from Eritrea, is the newest name on a roll call of young women whose friends and relatives believe they were tragically let down by the authorities.

Here are some of the others: Tania Moore, 26, was shot dead in Derbyshire by an ex-boyfriend after a campaign of harassment, which included threats to break her legs and gouge out her eyes. Bahnaz Mahmod, 20, was raped, tortured and murdered in south London by killers hired by her father and uncle, despite asking the police for help on six occasions. Clare Bernal, 22, who worked on the perfumery counter at Harvey Nichols in Knightsbridge, was shot dead by an obsessive ex-boyfriend who was on bail after threatening to kill her.

Now there is Arsema Dawit, whose family went to the police on 30 April to report that a man had slapped her in the face in a McDonald's fast-food outlet at Elephant and Castle and threatened to kill her. Last night a 21-year-old man from Ilford was charged with murder, but questions are being asked about why it took detectives 12 days to interview the schoolgirl about the alleged assault.

When a Safer Schools officer spoke to her on 12 May, Arsema reportedly denied all knowledge of the incident, prompting questions about the delay and why the interview was carried out at school. Detectives contacted her mother a week later and the investigation was continuing when she was knifed 10 times in a frenzied attack. In their defence, it has been said that officers were unaware of the claim that Arsema was being stalked and were having difficulty establishing the identity of her alleged assailant. But friends of the family say she was terrified and stopped going to the Eritrean Orthodox Church in Camberwell, where she sang in the choir, after the harassment began.

I can see a pattern. Time and time again, relatives of murdered women complain that the police responded too slowly, failed to take incidents seriously or simply did not believe that their daughters or sisters were being stalked. When a friend of mine was harassed by an ex-boyfriend who smashed plant-pots on her doorstep and punched her as she was approaching her flat, a police officer told her he was taking no action because it was "six of one and half a dozen of the other".

When I wrote to the police, expressing my concern and reminding them of the Home Office's own statistics – on average, two women are killed every week by a current or ex-partner – I received no answer. In the end, my friend moved to another area of London and the stalking stopped.

I don't think this is unusual. After Tania Moore's killer was jailed for life, a detective was sacked and five other officers disciplined after a police watchdog described Derbyshire police's investigation into the campaign of harassment against her as "abysmal".

When Bahnaz Mahmod tried desperately to get help, her fears that her family planned to kill her were dismissed by a policewoman who decided she was "dramatic and calculating". Clare Bernal had taken out a series of restraining orders against Michael Pech, the man who eventually shot her and then turned the gun on himself. Another woman, Uzma Rahan, was convinced that her husband was going to murder her. "Count the days before he kills me," she told relatives only days before he battered her and their two children to death with a rounders bat at their home in Cheadle Hulme, Greater Manchester.

Shafilea Ahmed, 17, was found with cuts and bruises in a park in Warrington, Cheshire, after she had been absent from school for more than a week, and told friends she had been imprisoned in her home by her family. The warning signs were not recognised; a year later she disappeared and her body was eventually found five months later in a flooded river in Cumbria.

What's striking about all these cases is that the women concerned knew they were in danger, perhaps even mortal danger, and made no secret of it. Some of them fit into the category of "honour" killings, others will have been recorded as instances of domestic violence or stalking, but the cumulative mistakes made by the authorities are grave when gender-based violence is so widespread. The Home Office knows that domestic violence is "chronically under reported" but admits that one incident is reported to the police every minute; it accounts for 16 per cent of all violent crime and will affect one in four women during their lifetime. Three-quarters of the victims are female and it has more repeat victims than any other crime.

These figures are bad enough, but a senior police officer astonished MPs earlier this year when he suggested that the incidence of forced marriage and honour-based crime might be 35 times higher than official figures suggest. Taken together, it paints a very bleak picture of levels of violence against women and the obstacles that victims face when they try to get protection.

It isn't as though the Government has failed to act, for the Domestic Violence, Crime and Victims Act 2004 was passed with the specific aim of increasing the protection, support and rights of victims; breaching a molestation order, for instance, is now a criminal rather than a civil offence. The Home Office has also drawn up a Domestic Violence National Action Plan to bring more perpetrators to justice.

So what is going wrong? A key factor seems to be the speed (or lack of it) with which police respond when a woman complains she is in danger; at present, investigation takes precedence over protection, and Clare Bernal's mother Tricia was absolutely right yesterday when she highlighted "the need for places where families can go to feel safe".

The other big problem is the culture of disbelief which is experienced by so many victims of gender-based violence, a category which includes rape as well as domestic violence and honour-based crime. When the rape conviction rape rate is as low as 5 per cent, why should we expect women who are being stalked and harassed to be treated any better by the authorities?

Despite the Government's efforts, there is entrenched scepticism about levels of violence towards women. I suspect that rank-and-file police officers are as sceptical as the rest of the population, and demoralised by their dealings with a cautious and ineffectual Crown Prosecution Service.

Bearing in mind how many women have correctly predicted their own murders, however, the case for abandoning this habit of doubting victims' testimony is overwhelming.