Olathe ? With more than three months left in 2010, Johnson County has already surpassed its record number of homicides.

Prosecutors say there have been 13 homicides in Johnson County so far this year. That compares with 10 last year and 11 in 1999, the previous record.

District Attorney Steve Howe said the average for 15 years through 2009 was just eight a year.

“Johnson County used to be a sleepy bedroom community without big-city problems,” he said. The county has grown to have about 500,000 residents.

Sex crimes also are up 5 percent this year. The increases come when homicides are down somewhat in Kansas City. As of Friday, Kansas City, Mo., had recorded 80 homicides, compared with 88 last year at that time.

Kansas City, Kan., had 22, compared with 28 a year earlier.

All the homicides in Johnson County this year have been cleared by police except the May shooting death of Shawnee liquor store owner Gerry Grovenburg.

Howe said the county’s crimes have included some “outrageous, improbable” ones. Among those was the June rape of a 92-year-old Leawood woman, and a September attack on a Prairie Village woman who survived after having her throat cut.

The economy could have a role in the growing number of crimes, Howe said.

“It seems to make sense that people under stress are more inclined to do things they wouldn’t ordinarily do,” he said.