Cortez Sims appears before Hamilton County Juvenile Court Judge Robert D. Philyaw for a detention hearing on Monday, Jan. 12, 2015.

Marcell Christopher was lying on his back, thinking he would die from the bullet in his chest, when the police officer approached him that early January morning.

"Who did this to you?" the officer asked.

Without hesitation, sources said, Christopher replied, "Cortez... Cortez Sims."

The officer's body camera captured it all.

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Cortez Sims

A few hours later, though, at the hospital, Christopher said something different. He told a Chattanooga Police Department investigator multiple times he couldn't remember who burst into the College Hill Courts apartment on Jan. 7, 2015, opening fire on him and three women.

Ordinarily, a prosecutor would be struck with a flip-flopping witness and a difficult case. But now, body cameras, security footage and even social media pages give authorities another digital lever to pull in court.

In this case, the footage was so powerful, sources said, it convinced a Hamilton County Juvenile Court judge to grant a search warrant. Officers tracked Sims to Knoxville and charged the then-17-year-old with one count of first-degree murder, two counts of using a firearm during a dangerous felony and three counts of attempted first-degree murder.

Local prosecutors could not comment on an ongoing case. But Steve Crump, the district attorney general for the 10th Judicial District who is not involved in the case, said the cameras add an extra dimension to investigations.

"I don't think they replace witnesses," Crump said. "But what it does change is how a prosecutor approaches a witness who is reluctant, or a witness who we believe is going to change their testimony. Looking at social media, where it's admissible, it is powerful evidence, too. Because just like the body camera footage, it is a person's own words. It is something a person typed on their Facebook page or their Twitter feed or their Snapchat story."

Several law enforcement officers said the footage crystallizes several issues surrounding witnesses who believe they will be killed for testifying in court.

"One thing that Bianca shows is we can't necessarily protect everybody, as much as we'd like to," said Chattanooga police Sgt. Josh May.

May, who directs the department's anti-gang violence efforts, was referring to Bianca Horton, the 26-year-old mother found shot to death on the 2100 block of Elder Street in late May. She and Christopher testified at a Juvenile Court hearing in 2015 to determine whether Sims should be tried as an adult, several sources said. Though officials were concerned she was killed in retaliation, they've never publicly confirmed it.

"That audio, that video, it may have helped us save this case," said Curtis Penney, a Chattanooga Police Department investigator. "Us understanding that Bianca can't be there to reiterate some of the things that went on, that's a little damaging. But this [identification] happening so close after the event itself, by someone who knows this person, saying it on camera, without hesitation it's huge."

The police department is in the process of outfitting all patrol officers with body cameras. The Chattanooga Housing Authority, whose on-scene officer recorded Christopher in 2015, has about 15 body cameras, said Felix Vess, the authority's police chief.

Vess extolled body cameras and the way technology allows law enforcement to work around difficult witnesses. He cited a 2012 gang shooting at College Hill Courts in which law enforcement used video of the event uploaded to YouTube to identify everyone involved.

"The victim was so scared, he didn't want to prosecute," Vess said. "But we actually got convictions based off the video."

In the Sims case, technology will play a big part, but so will gang violence.

Sims is an Athens Park Blood and Christopher a Bounty Hunter Blood, May said. The groups have feuded sporadically since January 2014, when an Athens Park Blood opened fire at 1501 E. 50th St., killing 13-year-old Deontrey Southers. Authorities believe the shooter was targeting his mother's boyfriend, a Bounty Hunter Blood.

Because of that backstory, gang intimidation presents a legitimate threat to Christopher testifying in Criminal Court, authorities said.

"He's agreed to [testify]," May said. "I think there's some caveats. He doesn't want cameras in the courtroom. He's doing really well. He's fallen off the radar. He got a job. Hopefully, he does the right thing."

It's unclear whether the body camera footage will be admitted into the Sims trial, now scheduled for Sept. 27. Either way, it's not as simple as Christopher skipping his appearance altogether, because defendants have a right to confront their witnesses.

There is the possibility of impeaching a witness, said Lee Davis, a defense attorney and former prosecutor. Impeaching witnesses means calling into question their credibility.

"Let's say they have the body camera footage [and then the witness] comes into court and doesn't want to say anything," Davis said. "Well, the prosecutor can still put that on."

The prosecutor could say, "Do you remember saying this? No? Well let me refresh your memory," Davis said. "And then, play the video in open court. Then ask questions: Do you remember what time? Build the circumstances. And ask, 'You heard yourself say [that], right?'

"They may be reluctant, but they'll say it."

The body camera footage can benefit either side because it preserves a fact at a moment in time, Davis pointed out. And it's the same every time, unlike human memory.

"I imagine it's pretty powerful, that image," Davis said. "And I know witnesses are reluctant, but sometimes a reluctant witness is the most damning witness because the jury understands — they're not saying it because they're scared or they don't want to be involved."

Contact staff writer Zack Peterson at Follow on Twitter @zackpeterson918.