MARIETTA — The 2010 crime statistics released by Cobb County and Marietta police departments and the FBI, reveal a mixed picture of crime trends in the past year.

In unincorporated Cobb, violent crime such as aggravated assault and rape increased, while murder and robbery slipped. Among property crimes, larceny rose, while burglary and auto thefts fell. In Marietta, murder and aggravated assault saw an increase, while robbery fell. Burglary and larceny rose, while auto thefts fell in the county’s largest city.

Murders in Cobb dropped by 31.6 percent from 19 in 2009 to 13 in 2010, while in Marietta, they rose from three to four.

While the overall number of murders was relatively low, police say it wasn’t low enough.

“Good news for Marietta would be no murders at all,” said Officer David Baldwin, Marietta police spokesman. “I can say that all four murders in 2010 were solved. Arrests were made in three of the cases, and the perpetrator in the fourth committed suicide.”

Perhaps the most notable murder case of 2010 was the Penske shooting. Cobb police arrested Jessie James Warren, who is accused of going on a shooting rampage that killed two workers and a customer at his former employer, Penske truck rentals in Kennesaw, on Jan. 12, 2010. He is awaiting trial.

While burglaries dropped by 4 percent to 3,291 cases in Cobb, they increased by 20.8 percent to 772 cases in Marietta.

Marietta police attributed last year’s spike in cases to burglary rings in the area, which they say have since been solved. Police broke up two to three rings of about 10 people, who ranged in age from their teens to 20s, mixed in with a few adults, Baldwin said.

“Some (were solved) by crime scene processing, some by the patrol units working with detectives, some by leads that were either given to us or developed by the detectives,” Baldwin said. “Basically, it was just very good police work.”

Aggravated assault and larceny increased in both Cobb and Marietta.

Aggravated assault rose by 18.5 percent, from 146 to 173 cases in Marietta. However, in the county it increased by 24.5 percent, from 576 to 717 cases in 2010.

“The only real way to find out the why would be to ask the perpetrators of the crimes,” Cobb police spokesman Michael Bowman said in response to why there was such a significant increase.

“Can crime be attributed to the economy? Can it be contributed to the job loss? Can it be attributed to complacency? There is no real answer as to why crime spikes or drops during a given year.”

Larceny, or theft of personal property, increased slightly in Cobb to 6,900 cases in 2010. But in Marietta, there was a 6.5 percent jump in larceny cases, which numbered 2,050 last year.

“There is nothing definitive that points to any main reason why there was an increase,” Baldwin said. “Some could be tied to the burglaries that were solved; you could speculate that the economy was part of the reason for the increase, although there is no direct evidence to prove that.”

Bowman said residents need to be more observant and learn to recognize what is suspicious and notify 911 when they encounter something out of the ordinary.

In 2010, there were 109 rape cases reported in the county, compared with 92 the previous year. The reported number of rape cases remained at 21 in Marietta.

Auto thefts declined in both Cobb and Marietta. With 834, the county experienced 224 fewer auto thefts in 2010. There were 49 fewer cases in Marietta, which reported 181 auto thefts during the same period.

Bowman said police officers are diligently patrolling the streets, subdivisions and businesses in the county.

“We would like to say that crime is on a decrease due to diligent patrol, but does that mean that if crime is increased, we are patrolling less? The answer to that question is no,” he said.

“Our officers are patrolling just as much now as they have in the past. Officers also have to change their patrolling techniques due to the increase of crime and increase in calls for service.”