A recent study in San Antonio, Texas shows that a full moon has no effect on the frequency of crime etc.

"Western lore has long suggested a relationship between the phases of the moon and various forms of aberrant, antisocial, deviant, and criminal human conduct," begins the Journal of Criminal Justice study led by criminologist Joseph Schafer of Southern Illinois University in Carbondale. "Policing, crime, and criminal justice have not been immune from speculation concerning the lunar-crime relationship."

So, to find out, the study team looked at San Antonio, Tex., from 2001 to 2005, a city of more than a million people for which exhaustive crime data is available. The team crunched nightly crime data, noting rain, daylight, indoor vs. outdoor locations and other environmental effects unaccounted for in past efforts. Murder happens too rarely in San Antonio to give a statistical signal, so the team looked at assaults, burglary, theft, drugs and vice crimes, traffic crimes, and "other disturbances," totaling about 130,000 incidents a year.

The study concludes. "Substantive lunar effects on crime were not found in the data analyzed here," say the report. "Although popular culture, folk lore, and even certain occupational lore suggested the 'freaks' come out during full moons, this phenomenon was not reflected in San Antonio police data as used here."

Instead, weekends and warm weather were linked to crime, as you might expect. Winter and rain decreased crimes, except in the city's Riverwalk entertainment district, home to bars, hotels, convention facilities, shops, and theaters, where the level of crime was the same regardless of conditions. The only slight effects of a full moon were a small increase in burglaries citywide, and a drop in vice arrests in the Riverwalk center, at the same time. Neither was statistically convincing, compared to weather or time of day.

But while the crime data don't show any lunar effects, that doesn't mean people aren't weirder during a full moon, the study authors acknowledge, something unlikely to come across in the dry language of a police report.

Link:
http://www.usatoday.com/tech/science/columnist/vergano/2010-07-11-moon-crime_N.htm