Murder is one of the crimes to be hated. Taking a human life cannot be permitted regardless of situations.
And the murder rate of each nation is various all over the world. Not surprisingly, Europe and Northern America are relatively safe regions. Of course, Japan is the safest country at least in the risk to be murdered.
On the other hand, Latin America is the deadliest region. A fourth of murder cases occur on this continent. And the murder rate seems not to be decreasing despite the civilization. Rather, according to the article below, rapid urbanization is one of the causes of increased murders.
The Economist: How to cut the murder rate
I agree with the opinion of this article. In some nations, police are not trustworthy, unfortunately. In such regions, the only reliable thing for you is yourself. Thus, if you cannot kill the enemy on your own, you will be killed.
Furthermore, gangs become powerful in regions where the police cannot be functional. Gangs deal with illegal drugs. And some drug-use is highly relevant to violent behaviors.
It seems that Colombia successfully reduced the murder rate by improving the reputation of the police. Making citizens trust the authority is an easy way to raise the level of social security.
Japanese are said not to trust the government, according to some questionnaire survey. I do not think so. Most Japanese never believe they would be tricked by the police. Rare cases of misconduct by the police are emotionally discussed in Japan. Silly.