In the second season of the BBC's hit show "Sherlock," shadowy snipers threaten the eponymous detective's friends by skulking around stairwells with high-powered rifles or infiltrating their homes and workplaces.

In real life, targets of assassination in Britain are more likely to be killed while walking their dogs or going shopping, new research finds.

The study of contract killings spanning from 1974 to 2013, published in The Howard Journal of Criminal Justice, finds that assassinations are often rather mundane.

"Hit men are familiar figures in films and video games, carrying out 'hits' in underworld bars or from the rooftops with expensive sniper rifles," David Wilson, a criminologist Birmingham City University's Center for Applied Criminology, said in a statement. "The reality could not be more different." [Understanding the 10 Most Destructive Human Behaviors]

The four types of hit men

Wilson and his colleagues were interested in studying contract killing, in which someone pays another person to carry out a murder. These types of killings are rarely studied, the researchers said.

They combed through newspaper archives for examples of hits in Britain and found evidence of 27 murders carried out by 35 hit men — and one hit woman. They also used court transcripts and interviews with offenders to find out details such as how much killers had been paid.

The results revealed a wide variety of ages and expertise in killing. Hit men were as young as 15 and as old as 63, with an average age of 38. There were four types of hit men: Novices, who were caught after their first murder; dilettantes, who are the least likely to have a criminal background and may lack enthusiasm for killing; journeymen, who are career criminals but not particularly stealthy; and masters.

Masters are the least likely to be caught, Wilson and his colleagues found. They often have a military or paramilitary background, and are successful because they have few local ties. Journeymen, in contrast, may be good at killing, but their criminal connections often give them away to police.

Motives for murder

The cost of a hit varies widely as well, the researchers found. The cheapest kill, in 2010, cost 200 British pounds ($331.72 in today's U.S. dollars), paid to Santre Sanchez Gayle, a 15-year-old, for killing 26-year-old Gulistan Subasi. Gayle was a "novice" hit man who was caught because he bragged about the killing later.

The highest fee for a contract killing was 100,000 pounds ($165,860 in today's U.S. dollars). The only female contract killer in the study, a New Zealander named Te Rangimaria Ngarimu, charged 7,000 pounds ($11,610 in today's dollars) to kill the business partner of two men who hired her from prison in 1992. According to news reports about her trial, she only received about one-seventh that amount.

One "dilettante" hit man, Orville Wright, became known as the hit man who lost his nerve. Wright was sentenced to two years in prison in 1998 after he threatened to kill a London woman at the behest of her ex-boyfriend. After breaking into the woman's flat and talking to her, Wright was unable to go through with the murder.

The tales hint at how pedestrian most contract killings are. While television hits usually involve shady conspiracies or megalomaniac masterminds, real contract kills are far less melodramatic.

"The motivations to pay a hit man the relatively small amount to carry out a murder were often depressingly banal," Wilson said in a statement. "Spouses fell out, business deals fell apart and young gang members wanted to impress their elders."

Or as Sherlock would say: "Boo-ooring."

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