Investigators: DNA from Georgia woman's murder leads to false twin

On July 18, 2008, Genai Coleman was sitting in her car near a bus stop reading her Bible when a man approached her with a gun.

The attacker, who came out of a gas station across the street, pointed his gun at her and ordered her to get out of her gold Dodge Stratus. He shot the 40-year-old in the chest, dragged her out of the vehicle and drove away.

Coleman, a resident of Gwinnett County, Georgia, did not make it.

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The murder is being investigated in Oxygen's true crime series “The Real Murders of Atlanta,” which examines “shocking, sinful and offensive cases” in the “metropolis of music, entertainment and technology” and features interviews with relatives, investigators and others connected to the cases covered.

Brittany Barrington, crime scene supervisor for the Gwinnett County Police Department, was on the scene.

“This is a crime of opportunity,” Barrington told Fox News Digital. “She did what people do every day, and I still do it sometimes – everyone does it. You just sit in your car and talk on the phone, not paying attention, just in a random parking lot. He took advantage of that. It's really a crime of opportunity. He needed her car and he wanted to take it.”

Coleman's family later contacted police, fearing that the punctual mother of three adopted children had never returned home. Investigators confirmed that Coleman was the victim.

As the episode reveals, Coleman was a popular teacher and an expectant grandmother.

Genai Coleman was a popular Georgia teacher and soon-to-be grandmother. Pictured here with a close friend. (Oxygen)

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Although Coleman had parked near a popular shopping center, the crime scene was “minimal,” Barrington said. There was a pool of blood and no suspect.

“All the important evidence that would have given immediate clues was gone,” she said. “What struck me was that the car was missing. There were no shell casings on the ground. And we knew a shot had been fired. That immediately raised my suspicion that maybe the shell casing had been left in the car. Maybe the shell casing had been picked up. Maybe the firearm used was a revolver, so no shell casings were left behind.”

There was a witness.

Genai Coleman was waiting for her daughter to come home from work when she was attacked by a stranger. (Oxygen)

According to the incident, a bus driver described seeing a man walk around the driver's side of the vehicle calling Coleman a “motherf—-r.” She heard a gunshot and saw the man pull Coleman out of the car and drop him to the ground.

Coleman's car was found in a parking lot about 40 miles away. A cigarette butt was found on the floor of the car.

“The slim chance of finding that cigarette butt provided a huge DNA lead,” Barrington said. “That quickly brought a whole new aspect of the investigation into play.”

The cigarette was submitted for DNA testing.

The episode also described how detectives reviewed surveillance footage and spotted a man purchasing a pack of cigarettes – Bronson Lights – at the gas station. The Bronson filters matched the filter they found in the recovered cigarette butt. The same man was also seen walking through a parking lot approximately 15 feet from where the vehicle was parked.

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A cigarette butt was found in Genai Coleman's car. Family members confirmed that Coleman was not a smoker. (Oxygen)

The DNA results were in. They led to Donald Smith.

Investigators said Smith had previously been charged with armed robbery, making him a “clear suspect.” They obtained his cell phone records and found that his phone had been beeping cell towers near the crime scene the night the murder occurred. He also looked exactly like the man spotted on the security camera.

Police were confident they had caught her killer. But when Smith was brought in for questioning, he insisted he had never seen Coleman or her car. When police told him they had his DNA, Smith replied, “So what?”

“My DNA couldn't have been in that car because I was never in that car,” Smith said.

A witness, a bus driver, heard a gunshot. Then she saw Genai Coleman being dragged out of her car by a man. (Oxygen)

Smith was then shown the surveillance footage.

“That’s definitely not me,” he said.

Smith went on to say that the cell phone number found by police was that of his brother – an identical twin.

“Donald and Ronald – he’s my twin,” Smith said.

Barrington said murder cases involving identical twins are “extremely rare.”

“This is the only major homicide the department has had involving identical twins,” she explained. “I haven't had another crime scene involving identical twins since then. This was a unique experience. … You don't usually have something like this. Usually it's a single person, or you have twins, but fraternal twins. But the uniqueness of identical twins is very rare.”

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The fingerprints discovered by police belonged to Ronald Smith. (Oxygen)

Smith initially refused to implicate his brother, Ronald Smith, who also lived in Gwinnett County, but later confirmed that the man in the surveillance video was Ronald.

In addition to the cigarette butt, fingerprints were also found in the car. These would be the key to finding out which twin did it.

“Even if you're an identical twin, you're going to have unique fingerprints that distinguish you from your sibling,” Barrington said. “That helped us figure out which brother had his hands on the roof of Genai's car, so we could determine which brother was the real suspect.”

The fingerprints matched Ronald.

Ronald, who was arrested, later admitted to killing Coleman and taking her car before abandoning it, claiming the shooting was “an accident.”

“It was a light trigger pull,” Ronald claimed, as the Oxygen series shows. “I was trying to steal a car… at gunpoint. The shot went off.”

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In October 2012, Ronald was convicted of murder, first-degree murder, aggravated assault, auto theft and possession of a weapon during the commission of a felony. The Gwinnett Daily Post reported that he was sentenced to life in prison plus 25 years.

Barrington said such a crime could “happen to anyone, at any time.”

“Be aware of your surroundings,” she warned. “And also be aware that detectives, police and all other investigators are passionate about justice. They want to help.”

“It takes an emotional toll,” Barrington reflected. “It also takes a professional toll. But that's why we're here. That's why we exist.”