Almost half a million people were murdered in 2012, showed an official tally from the United Nations Office on Drugs and Crimes (UNODC).

More than half of all murderers in Sweden had consumed alcohol, the report noted. Alcohol could explain why murder rates were higher in northern Sweden compared to the rest of the country. On the regional map, there were also quite different murder rates in various parts of neighbouring Finland.

"Available data indicate that this phenomenon – higher homicide rates in certain parts of northern Europe – is associated with patterns of alcohol consumption, among other factors," the report noted.

In layman's terms, the more often people get drunk, the bigger the risk of murder. In Sweden, 20 percent of male perpetrators had taken drugs. 

"The consumption of alcohol and/or illicit drugs increases one's risk of becoming a victim or perpetrator of violence," the report noted. "In Sweden and Finland, for example, over half of all homicide offenders were intoxicated with alcohol when they committed homicide."

In fact, 82 percent of Finnish murderers were drunk at the time of the killing, a much higher rate than in Sweden, which researchers also said could explain why more murders per capita took place in Finland than in Sweden.

Most murderers globally used a gun to kill their victim, but in Europe gun-related homicides were much less frequent than elsewhere in the world. Thirteen percent of European murders involved a gun, while 33 percent involved a knife or other sharp instrument. In the Americas, in contrast, two out of three murders involved a gun, and knives only claimed 17 percent of the murders. 

UNODC also looked at the different types of murders worldwide, whether they involved couples, for example, or were ordered hits.

Looking at statistics from 2003 to 2006, mafia murders accounted for 11 percent of killings in Sweden, while another six percent were connected to robberies or other criminal acts. Fourteen percent of murders involved people who knew each other previously, while almost one in three (28 percent) of the killings had taken place for unknown reasons.

Forty percent of Swedish murders were recorded cases of fatal domestic violence, a high percentage compared to the global average of 15 percent. Worldwide in 2012, there were 63,600 recorded cases of people dying at the hands of a partner, ex-partner or family member. Seventy percent of the victims were women.

"Home can be the most dangerous place for a woman,” said Jean-Luc Lemahieu, UNODC director for policy analysis.