Gainesville’s last murder mystery occurred more than four years ago, on Memorial Day 2006, when police found the body of a 23-year-old man in the stairwell of a Summit Street apartment, dead of a gunshot wound to the chest.

The murder of Raul Rodriguez at Lanier Terrace Apartments remains unsolved, but the 13 homicides that have occurred in Gainesville and Hall County since then, including a shooting last month on Patterson Drive, have all been cleared with an arrest or arrest warrant.

Gainesville and Hall County’s 100 percent clearance rate for homicides in the past four years and three months is made even more remarkable by the national average solve rate of 63.6 percent.

“I think the public getting involved more, the advanced training our officers have had in death investigations and everybody working as a team, no matter what the jurisdiction, has really helped to solve these crimes,” said Gainesville Police Lt. Carol Martin.

Murder is a legal term; if a defendant doesn’t plead guilty in court, it’s up to a jury, or in some cases a judge, to determine whether he or she is guilty. But law enforcement officials consider a homicide solved as soon as a judge issues an arrest warrant, whether the suspect is ever convicted in court or even captured.

Counting the June 26 arrest of 39-year-old Valentin Garcia in the shooting death of 26-year-old Santamaria Avelar, Hall County Sheriff’s authorities have cleared every homicide case they have investigated since April 2005.

The fatal shooting of 37-year-old cab driver Jose Javier, whose body was found dumped in a secluded area off Winder Highway on April 4, 2005, remains unsolved.

Experts and law enforcement veterans say good homicide solve rates depend on a number of factors: the cooperation of witnesses, the relationship between the victim and perpetrator and whether drugs were involved.

One of the top factors is the level of police response, according to “Clearing Up Homicide Clearance Rates,” a research paper authored by Dr. Charles Wellford, a criminal justice professor at the University of Maryland.

“The number of detectives assigned to a case is particularly important,” Wellford wrote. “Assigning a minimum of three detectives and perhaps four appears to increase the likelihood of clearing it. ... The length of time it takes detectives to arrive at the scene is also key. Cases in which the detective arrived within 30 minutes were more likely to be cleared.”

Both the Hall County Sheriff’s Office and Gainesville Police Department take a “flood the zone” approach when it comes to homicides.

“It’s important to contribute as many resources to these the types of incidents as possible,” said Gainesville Police Chief Brian Kelly. “The first 48 hours are the most crucial in an investigation of this type.”

Kelly said a “saturation” of the area by uniformed officers, investigators and crime scene technicians is standard procedure in homicides.

“Investigations of these types are very taxing on all involved and they have the potential to grow quickly,” he said. “It is a must that the proper amount of resources and supervision are allocated.”

Hall County Sheriff’s Col. Jeff Strickland echoed the chief’s comments on investigating homicides.

“We don’t just have one investigator investigating a homicide, we have a whole team,” Strickland said. “We bring out a team of investigators and we work very hard around the clock running down all the leads.”

Hall County District Attorney Lee Darragh praised the two agencies’ records of solving homicides.

“Both have excellent criminal investigation divisions,” Darragh said. “The officers aggressively pursue leads in a thoughtful, professional manner. Our community can be proud of these agencies, as well as the other law enforcement agencies in our circuit.”

Both Martin and Strickland acknowledged that besides hard work, witness cooperation and advances in forensic sciences, luck can play a role in breaking a case.

And Strickland said while it’s good to have a winning streak, they realize it could come to an end.

“We’re proud of the job we’ve done, but we acknowledge the fact that homicide cases are very difficult to solve,” Strickland said. “We hope that we’re successful in the future, but sometimes, when there’s little evidence and no witnesses, they are very difficult.”