Conclusion / Why

When I analyze a cause and effect argument in this way: Conclusion: the blame for this rise in homicide in the 1980s in Britain falls on the permissiveness of the government for allowing such lethal weapons to be sold. Why? The weapon used usually was a knife and potentially lethal knives are sold openly and legally in many shops. And we know that most deaths occur as a result of unpremeditated assaults within the family. Which is the cause and which is the effect?