Feb. 22, 2010— -- When police arrested Donald Smith for the 2008 carjacking and murder of a preschool teacher in Gwinnett, Ga., it seemed certain they had the right man. Smith matched witness descriptions, he seemed to appear on nearby surveillance camera footage and there was DNA evidence apparently proving he was at the scene of the crime.
Throughout it all, though, Donald Smith earnestly claimed that he didn't do it and instead offered an usual defense. He said his identical twin brother, Ronald Smith, was to blame, according to police.
When investigators followed up on Donald's claim, they found a trump card in his favor among a battery of other evidence: Fingerprints at the scene of the crime did not belong to Donald but to Ronald Smith. Even though identical twins share the exact same DNA, they do not share the same fingerprints.
After he was presented with the evidence against him, Ronald Smith admitted to the crime, police said. Ronald's attorney, Lawrence Lewis, said he has need seen the alleged confession and maintains his client's innocence.
"This is an unusual case," Gwinnett County Police Cpl. David Schiralli told ABC News. "No. 1, I'm glad that we were able to find the right brother and that we were able to find evidence to exonerate the other brother. Our investigators were faced with a tough task, dealing with identical twins."
In a justice system that often relies heavily on high-tech DNA testing, it was fingerprinting, a practice more than a century old, that succeeded where DNA failed.
It's thanks to a very similar case from 107 years ago that fingerprinting is today just as critical to investigations as the much newer DNA evidence.
At the turn of the 20th century, investigators had tinkered with fingerprinting, but the technique was not widely used, according to the FBI archives.
Rather, to identify suspects, investigators relied on the much-trusted Bertillon system, which "measured dozens of features of a criminal's face and body and recorded the series of precise numbers on a large card along with a photograph," FBI records said.