MARIETTA, Ga. -

Eighteen-year-old De'Marquise Elkins was found guilty of malice murder, felony murder and all other counts Friday afternoon in the killing of 13-month-old Antonio Santiago in a stroller on a Brunswick sidewalk in March.

Karimah Elkins (pictured, below), the teen's mother who was on trial alongside him, was found guilty of tampering with evidence and not guilty of making a false statement.

De'Marquise Elkins' other charges included attempted felony murder, aggravated assault, criminal attempt to commit armed robbery, cruelty to children, possession of a firearm during the commission of a felony.

The 12-person Cobb County jury deliberated for about two hours after listening to the two-week trial.

"There were no winners in the courtroom today," said Kevin Gough, De'Marquise Elkins' attorney. "While the defense has the utmost respect for the court, we take exception to critical evidence being withheld from the jury, depriving our client of a fair trial."

Gough said he will appeal the conviction and fully expects to retry the case.

"Mr. Elkins will eventually be exonerated," Gough said.

Prosecutors said Elkins killed Antonio in an attempted robbery. The baby's mother, Sherry West, was also shot.

De'Marquise Elkins' defense attorney told the jury the investigation was flawed and police ignored other leads and suspects -- raising questions about the mental stability of the victim's mother, Sherry West -- while the prosecution said witnesses may have had shifting stories but video and other evidence doesn't lie.

"Maybe she (Sherry West) has some mental health issues. It doesn't make her a liar," Glynn County District Attorney Jackie Johnson (pictured, right) told the jury.

Elkins now faces life in prison. At the time of the shooting he was 17, too young to face the death penalty if convicted under Georgia law.

As for Karimah Elkins, her attorney also addressed the jury during closing arguments.

"Did they Mirandize her? No. Not one officer Mirandized her," said Wrix McILvaine, the defense attorney for Karimah Elkins. "The judge will instruct you that if you find that she was in detention and wasn't free to leave that she needed to be Mirandized before she was questioned if you are to consider anything she says, that you have the right to remain silent, the right to have counsel the right to have counsel with her at all times before and after questioning and during questioning. She had the right to be told if she said anything that it would be used against her in the court of law."

Tim Pulliam Tweets From Courtroom

The trial was held in an Atlanta suburb because of pretrial publicity.

Another teen, 15-year-old Dominique Lang, also faces murder and other charges in the case. He's set to be tried at a later date.

Gough asked Santiago if he had any reason to testify in a way that is favorable to the state’s case. When Santiago said he didn’t, Gough asked whether he had any pending criminal charges brought by the district attorney’s office. Santiago testified that he has a pending charge for aggravated stalking.

Gough strongly suggested in pretrial motions that the real killers are the child’s own parents. He has made several suggestions to the same effect during the trial. But much of his questioning that seemed to be heading in that direction – including attempts to bring up details about the backgrounds of both of the baby’s parents – has been blocked by the judge.

Santiago testified that on the morning of the shooting he, Karen, and William left their apartment building to drop William off at his job at T.J. Maxx. Santiago said he picked out juices and snacks for his young son. When the pair was at the checkout, Santiago got a call from a detective telling him his son had been shot, he testified. He and Karen ran out of the store without the groceries and drove to the hospital, he said.

Prosecutors say Elkins and an accomplice, 15-year-old Dominique Lang, stopped Sherry West as she walked home from the post office and demanded money. When she refused to hand over her purse, the older teen shot her in the leg and then shot the baby.

Prosecutors have said information from Elkins’ mother and sister led investigators to a pond where they found a revolver. Elkins’ sister also was charged with evidence tampering.

Prosecutors also have accused De’Marquise Elkins of shooting a pastor during an attempted robbery outside a church in Brunswick 10 days before the baby was killed.

An expert on eyewitness identification testified earlier Thursday that the photo lineups of suspects in both the pastor’s shooting and the baby’s slaying were suggestive.

Georgia State University cognitive psychology professor Heather Kleider said the photo lineup shown to West was suggestive because the men in the photos had distinctly different physical characteristics and not all of them matched a description of the shooter given by West. She said the lineups given to the pastor and another man had similar problems.

The defense also called a string of witnesses whose testimony seemed intended to cast doubt on prosecution witness testimony, and to question the thoroughness of the investigation into the baby’s killing.

One was Argie Brooks, a man who approached police Capt. Wan Thorpe the day of the shooting saying he had information about the killing. Brooks told Thorpe he lived with the aunt of the boy who shot the baby and that he needed money to buy crack cocaine to get the aunt high, Thorpe testified.

Thorpe declined to give Brooks money for crack but told him about reward money available in the case, Thorpe said. Brooks asked for a computer to identify the shooter and when Thorpe brought him one, he pulled up a mug shot of someone named Dominique Elkins, Thorpe said. When told that Dominique Elkins was in jail at the time, Brooks said he knew it was someone named Elkins and told Thorpe that if he had money to buy crack for the aunt he could “get old girl loose” and get more information, Thorpe testified.

The woman Brooks was living with was Debra Obey, who is the aunt of Dominique Lang, De’Marquise Elkins’ co-defendant.

Brooks testified that he got $2,000 from police for information he provided and had a written agreement signed by the police chief and someone else that said he’d get an additional $8,000 if Elkins was convicted. Gough told the judge it was important to hear from Brooks because he was a witness paid by the state.