Repeat offenders and the Kevin Bacon effect

According to La Mesa police chief Ed Aceves, a joint project between the La Mesa Police Department and San Diego County Sheriff's Department that targeted "prolific offenders" resulted in a 45 percent reduction in residential burglaries and a 51 percent reduction in vehicle burglaries between February and April.

Aceves said that the Sheriff Department's Statistical Analysis Driven Law Enforcement Team (SADLE) worked with his department on a logistics-driven way to stop crime.

"It's not how it's typically done in law enforcement; the normal approach is, ‘Let's work with the area where there's a lot of crime,’” Aceves explained. "Instead, the approach was focusing on the prolific offenders in our area."

Prolific offenders are people with convictions for burglaries, and they're generally out on parole or probation, which gives cops latitude in stopping and searching them — in cop language, “4th waivers.”

"We started with the top 100 offenders in our area. Most have been arrested in the last three months," Aceves said. "We target these people — in some cases we followed them."

The project included Rancho San Diego and Spring Valley, where the sheriff has jurisdiction, as well as La Mesa. The data team looked at patterns, including location and times of day of burglaries, and tied it to offenders.

For example, an area of apartment and condo complexes along Baltimore Drive north of Aztec Drive had a lot of vehicle burglaries, he said.

"If there's 50 vehicle burglaries, it isn't 50 random events, it's a small group of offenders," a SADLE spokesman said. "Prolific offenders are a small percentage of people committing a large percentage of crimes."

Not only did the cops target the prolific offenders, they targeted the offenders' associates. And they tied the offenders and their friends to hotspots for burglaries.

"It becomes the family tree drawn on the wall. Everyone is somehow connected — the prolific offenders are connected. It's like the Kevin Bacon game of prolific offenders," Aceves said.

For example, La Mesa had a series of residential burglaries in one area and DNA evidence identified a single unknown suspect — who turned out to be an associate of a prolific offender.

"We had several hotspots where there were a series of burglaries, the same M.O., the same time of day, that made us think the area was familiar to the offender," Aceves said.

"Typically, we find friends [of a prolific offender] live in the area where that's happening."