DECATUR — Budget woes have tossed a proverbial wrench in the assembly line of crime lab reports generated by the Georgia Bureau of Investigation, and criminal prosecution in Gwinnett is feeling the effects.

Three of the GBI’s seven branch laboratories — in Columbus, Summerville and Moultrie in south Georgia — are slated to close March 31. Officials are mulling an 8 percent trim to a crime lab budget that recently stood at $19.1 million.

“It has been a bloodbath shutting these three laboratories,” GBI director Vernon Keenan said.

The Gwinnett County District Attorney’s Office relies on the GBI for testing in nearly every criminal case, from alleged crimes involving blood-alcohol levels to bullet residue. The lone exception is misdemeanor marijuana cases, said District Attorney Danny Porter.

The GBI’s backlog in January was 5,700 cases — a figure expected to swell to 8,420 in three years — which officials say is a direct result of budget constraints.

The backlog, coupled with a rise in the sheer number of Gwinnett cases, has increasingly gummed prosecution in Gwinnett since about 2005, especially in drug cases, Porter said.

Most worrisome, Porter said, is that the science required to prosecute some high-profile crimes has taken a particular hit.

Porter didn’t venture to guess how many Gwinnett cases are hinging on GBI crime lab reports.

“The crime lab has had to concentrate services into the high demand areas in order to keep the backlog manageable,” Porter said. “That means that certain services, such as fiber and hair analysis, handwriting and certain aspects of DNA analysis have suffered.”

The GBI has retained 136 scientists, including 14 medical examiners dotted around Georgia, which indicates the agency’s crime-processing capabilities are not “in a meltdown,” Keenan assured journalists during a recent tour of GBI’s Decatur headquarters. As with many government agencies, the topic du jour was budget constraints.

But backlog statistics may paint an unrealistically grim picture. District attorneys can request that cases be expedited by placing a phone call to GBI headquarters, said spokesman John Bankhead.

“We’ve gotten some unfair criticism over that,” Bankhead said.

Keenan concurred, adding the GBI has played “whipping boy” in certain cases district attorneys aren’t interested in moving forward with. Eighty-eight percent of crime lab reports are still completed in 90 days, he said.

“Our goal is 30 days,” he said.

Some crime-related tidbits gathered from a recent GBI tour:

• Georgia is cocaine country. In most counties, the drug is three times more prevalent than methamphetamine, crime lab director Dr. George Herrin said. Numbers suggest oxycodone use is spiking, he said.

• The GBI handles autopsies for all but seven of Georgia’s 159 counties, excluding larger metro counties like Gwinnett and Fulton. On average, it processes 3,500 autopsies per year, each taking about 60 minutes.

Dr. Kris Sperry, Georgia’s chief medical examiner, said about seven bodies per year are submitted as suicides but leave as homicides.

• Hair/fiber testing costs about $2,500 per case, the most expensive examinations the GBI provides.

• Processing each DNA sample costs about $20. More than 1,700 cases have been solved in Georgia using a FBI computer software program called CODIS that links suspects to evidence left at other crime scenes, Herrin said.

• In 2007-08, 67 percent of Georgia’s drug-related deaths involved prescription medication. Most victims were white and middle-aged, said Keenan, the GBI director.

• The GBI’s bomb unit is among the busiest in the country, with about four activations per week, Keenan said.

• GBI evidence deemed unnecessary is fed to a big incinerator “out back,” Herrin said.