(CBS) -- There's no question Ronald Johnson was running from Chicago Police in October 2014, before he was shot dead in the back by an officer.
But did Johnson, 25, have a gun?
Three years later, that's the question still swirling around his death.
Anita Alvarez, the Cook County state's attorney at the time, declined to criminally charge the officer who shot Johnson. The reason, she said in a nationally televised press conference in December 2015, was because evidence showed Johnson was armed.
That evidence included grainy police dashboard video, which had been sent to the FBI's Regional Computer Forensics Laboratory to be enhanced.
Alvarez said the enhanced video appeared to show Johnson holding a gun.
But now, a forensic video analyst tells 2 Investigator Brad Edwards that the video was resized incorrectly, possibly producing a false image.
"If the question is what was in his hand, the answer should be, 'We can't tell,'" Grant Fredericks, the analyst, tells Edwards.
Fredericks says the FBI lab made a series of errors that, in part, stretched the pixels and ultimately fabricated the shape of a gun.
"It's a false image," he says.
Fredericks viewed the video at the request of Michael Oppenheimer, an attorney representing Johnson's mother in a civil lawsuit against the city.
"We don't make these allegations lightly," Oppenheimer says. "Nobody has told us we got it wrong."
The 2 Investigators asked Alvarez, the Emanuel Administration and the FBI to discuss Fredericks' findings on camera. All said no.
The officer who fatally shot Johnson was cleared partly because all the evidence showed Johnson was armed. Police said they found a Browning 9-millimeter pistol in his hand.
Tests revealed a drop of Johnson's blood was on the weapon. But his fingerprints were not. Oppenheimer claims police planted the weapon.
"How in the world, unless that gun is glued to his hand, is it staying in his hand after he fell," the attorney says. "I simply don't believe it."
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