BBC News Online examines the complicated world of so-called honour crimes, who it affects and the problems authorities face in stopping it happening.
What is honour killing?
Honour killing is a complex but brutal reaction within a family against someone who is perceived to have brought "shame" upon relatives.
Although cases are rare, it is a problem that continues to this day predominantly in south Asian and Middle Eastern countries - and their diaspora around the world.
What constitutes this dishonour depends entirely on the family involved - but experts in the field say it can be anything from wearing clothes or choosing a career which the family disapprove of, to marrying outside of the wider community.
As with the majority of bitter family rows, a dispute may just end with relatives never speaking to each other again.
But in the extreme circumstances seen in honour crimes, the person believed to have brought the "dishonour" upon the family is murdered.
The majority of victims are women in communities or families dominated by men, although women - sisters and mothers - also play a part in some of the crimes.
So what constitutes honour? Is this is a religious issue?
No. The world's major religions do not play a part in these killings - although many of the guilty have tried to justify their actions on religious grounds.
The key factors are cultural and generational divisions, the victim's refusal to toe a line and a reaction against a family or clan's self-proclaimed code or rules.
In that sense, honour killings are much more about male-dominated societies or communities that try to stop women taking their own decisions. In other words, the killers believe it is culturally acceptable for them to murder to preserve, in their mind, the good name of the family.
More recently, in the age of migration around the world, the murders have come where a family reacts violently to a son or daughter taking on the trappings of a western culture.
For instance, accusations of dishonour may emerge because someone from an older migrant generation remains utterly tied to the culture or code of their village - and fails to accept their children have been brought up in modern British society with all that goes with that.
Crucially, the number of people who believe that violence in the name of honour is justified is very, very small.
What's the UK's experience?
Police believe there may be 12 honour killings a year in the UK.
One of the most horrific and well publicised cases of recent years was that of 16-year-old Heshu Yones, a teenage girl in a Kurdish family in London.
In 2002 Heshu's father Abdullah stabbed her to death because he disapproved of her Western dress and Christian boyfriend.
He then attempted suicide and at his 2003 murder trial appealed to the judge to sentence him to death.
What do we know about the size of the problem internationally?
It's impossible to know how widespread it is around the world - not least because in many cases it involves a cover-up by other family members or a wider community.
Sometimes, however, crimes are committed publicly. In one recent case in Jordan, a man walked into hospital and shot dead his unmarried cousin after she had just had a baby. He promptly surrendered to police and declared he had killed her to "cleanse his family's honour".
Jordan's Queen Rania continues to lead a campaign against honour killings in the country - though politicians there and elsewhere have been reluctant to introduce tougher sanctions for murders where family honour is a motive.
Do many of the crimes remain uncovered?
That's what campaigners have long argued. In their 1997 book, Leeds-born Jack and Zena Briggs (not their real names) described how they had spent years on the run because her family violent opposed their relationship.
Zena, from a Pakistani family, had been promised to a Kashmiri hill farmer - but when the family discovered her relationship with Jack, they were relentlessly pursued.
Zena's father told her she was "already dead" in his eyes while her sister predicted they would end up in "bin bags". Jack's mother was terrorised by people looking for the young lovers.
One of the key themes of the book is how the couple felt the authorities had failed to help.
Critics say that in the past many agencies have been reluctant to act against honour disputes because they have either completely failed to understand the culture or decided not to get involved on wholly-misguided grounds of "cultural sensitivities".
So how are the authorities trying to tackle honour crimes?
The murder of Heshu Yones triggered today's continuing police investigation into the warning signs of honour crimes.
The team set up by Metropolitan Police, but involving officers around the country, are examining 100 murders from the last decade in an effort to better understand and predict the signs of a potential honour killing or ongoing abuse.
They are also looking at other factors such as rates of domestic violence. Campaigners also want them to look at suicide, saying the disproportionately high rate of self harm among British Asian women can be linked to honour disputes.
The police say the most important change they have made is to tell officers to treat reports of honour crimes the same way as they are supposed to treat domestic violence - even if there is no clear evidence, it should be investigated.
What about international developments?
There is now an acknowledgement that honour crimes in the UK can be linked to those in other parts of Europe and that police forces around the continent must learn from each other.
In some cases families are believed to have hired foreign bounty hunters or contract killers. These individuals come into a country, kill the victim and then quickly disappear back into the countries they came from.
Some honour killings also involve sending the victim back to the family's "home nation" to be killed there, a crime that may never be reported.
These cases have proved extremely difficult to investigate in the past, especially if the local police authorities are reluctant to get involved.
And what about communities themselves?
Ram Gidoomal of the South Asian Development Partnership has campaigned for years for people to open up and turn in those who get away with justifying honour crimes.
He has consistently called on leaders in mosques, temples and churches to do more - but also says that other communities need to act if they pick up the warning signs.
In particular, he cites the role of schools and social services who may be the first to identify that a teenager is facing family problems.