Almost everyone who commits murder in Japan gets caught:
Japan maintains near-perfect homicide clearance rates (around 95%, compared with roughly 60% in the United States).
Of course, there are reasons for this. The types of murder committed in Japan are different:
This study explored possible explanations for higher homicide clearance rates in Japan than in the United States. Using recent (2000 to 2004) official summary statistics, this study found that Japanese homicides contain a higher proportion of “easy-to-clear” cases, including those with nonfirearm weapons, family member offenders, and child (and not teenager or young adult) victims, than do American homicides.
And how the Japanese classify a “homicide” differs as well:
Also the Japanese categorization of homicides in official statistics includes cases favorable to clearance (attempted homicide) and excludes cases unfavorable to clearance (robbery-homicide). These findings suggest caution in attributing Japan’s higher homicide clearance rates exclusively to police effectiveness or citizen–police cooperation. Suggestions for future multivariate research are also discussed.
Source: “Explaining Differences in Homicide Clearance Rates Between Japan and the United States” from Homicide Studies February 2008 vol. 12 no. 1 136-145
So when you factor all that in, maybe Japan isn’t such a bad place to be a homicidal maniac. Not so fast. The cops would likely have plenty of time and manpower with which to find you because they’re not all that busy:
Japan’s homicide rate dropped 70% in the last 50 years, and the nation now has one of the lowest homicide rates in the world. A decline of this magnitude has been documented in few other contemporary social settings.
Normally it’s a pretty simple formula: young men = more crime and murder. Oddly, not in Japan:
One key feature of the fall is young Japanese males, who now commit one tenth as many homicides as their counterparts did in 1955. At present, Japan’s homicide rate is higher among men in their 50s than among males aged 20 to 24. This article describes Japan’s postwar homicide decline and the vanishing young killer in particular. More is known about who is responsible for the decline than about what has caused it. The search for a more satisfying explanation of Japan’s homicide drop should be a high priority in homicide studies.
Source: “The Homicide Drop in Postwar Japan” from Homicide Studies, February 2008, vol. 12 no. 1 146-160
If you’re curious about this kind of stuff you really should read: You just committed murder. What should you do now?