Prison records show that Karl Smith, a ward of the Chicago prison system, has a tattoo of a skull with a top hat on his left upper arm which also includes the words, “Trust me.”

Prosecutors found that hard to do last week as Smith, 38, sat in a courtroom and confessed to a 2003 murder for which his identical twin brother, Kevin Dugar, has served 13 years in prison.

"I'm here to confess to a crime I committed that he was wrongly accused of," Smith testified, according to the Chicago Tribune.

Dugar, who had not seen his brother in years, sat nearby and wiped tears from his eyes.

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Cook County prosecutors were dubious about Smith’s claim, pointing out that he only came forward after an appeals court denied his bid to toss out his own attempted murder conviction for a separate crime. Smith is serving 99 years for his part in a home invasion and armed robbery that left a 6-year-old boy shot in the head.

"He's got nothing to lose," Assistant State's Attorney Carol Rogala said of Smith’s confession.

The Tribune reported that Rogala argued that Smith's confession didn't fit "independent eyewitness accounts of what happened."

It is unclear when the judge in the case will decide whether or not Dugar will be granted a new trial.

Those who know the twins told the Tribune that they were closer than siblings growing up, sharing everything – clothes, food and each other’s names. Their mother, Judy Dugar, said that even she and their father, who died last month, couldn’t always tell them apart. In court, only their uniforms, from separate prison facilities, distinguished the two.

Both standing 5 feet 9 inches tall, just 5 pounds separates the brothers, Illinois Department of Corrections records show. They both keep their hair cropped close to their heads and trim their beards in nearly identical patterns.

Different tattoos, and healed gunshot wounds on Dugar’s right hip, also mark who is who.

The Tribune reported that the twins' mother wept as Smith, who took her maiden name in adulthood, confessed to murder. It was the first time in several years that she and her sons were in the same room together.

Smith confessed to a March 2003 shooting near Sheridan Road and Argyle Street in Chicago that killed Antwan Carter and wounded a second person, Ronnie Bolden. The Tribune reported that Bolden testified at Dugar’s 2005 trial that the gunman was “Twin,” the street name used by both Smith and Dugar, who often impersonated each other.

Drug dealers and gang members at the time, the brothers would use one another’s names interchangeably. Smith testified last week that he was stopped by police shortly after Carter’s murder, but was allowed to leave after identifying himself as his brother.

Bolden, a member of a rival gang, testified at Dugar's murder trial that he initially didn't identify Dugar as the gunman because he wanted to settle it himself on the street, the Tribune reported. He eventually identified Dugar in a photo lineup that did not include Smith.

A second witness, a 16-year-old girl, recanted her testimony at the trial, saying that she identified Dugar as the gunman after Bolden told her to. Based largely on those eyewitness statements, Dugar was convicted of first-degree murder and sentenced to 54 years in prison.

Smith testified that he kept his secret to himself until 2013, a decade after the slaying, the Tribune reported. At that time, he sat down in his cell at Menard Correctional Center, in Pontiac, and wrote to his brother, who was housed in Stateville Correctional.

"I have to get it off my chest before it kills me," Smith wrote. "So I'll just come clean and pray you can forgive me. I'm the one who and shot and killed those two Black Stones on Sheridan that night."

Dugar didn't respond to that first letter, the Tribune reported. When Smith wrote a second letter a few weeks later, he responded and asked his brother to write to his attorney.

Smith ended up signing a sworn statement in 2014 in which he confessed to the murder.

Now that the case has seen the inside of a courtroom, the twins’ mother hopes at least one of her sons will gain his freedom.

"I hope Kevin will get out. I hope he change his whole life around," Judy Dugar told the Tribune, crying. "He got to."