Fort Lauderdale, Florida (CNN) -- A Florida teenager attacked and set on fire last month, allegedly by five teenage friends, was undergoing skin graft surgery Friday, the first procedure in his recovery, a hospital spokeswoman said.
Michael Brewer, who suffered burns over 65 percent of his body, will have his own skin transplanted onto the burned areas of his back and buttocks, said Lorraine Nelson, a spokeswoman at the University of Miami's Jackson Memorial Hospital Burn Center.
Brewer will return to the intensive care unit after the surgery. He has been heavily sedated since the October 12 incident and on a ventilator until last week to keep him alive.
He is listed in guarded condition.
On Thursday, three teens accused of setting Brewer on fire pleaded not guilty to charges of attempted murder, a public defender for one of the boys said.
Each of the three -- Denver Jarvis and Matthew Bent, both 15, and Jesus Mendez, 16 -- is charged as an adult with one count of attempted murder in the second degree in the attack in Deerfield Beach, Florida.
They were arraigned in Broward County Circuit Court before Judge Dale Cohen, and are being held without bond.
Prosecutors say the three boys were in a gang that poured alcohol over Brewer, then set him ablaze in a dispute over $40, a video game and a bicycle.
Gordon Weekes, Bent's attorney, denounced the fact that the teens were charged as adults.
"It's been decided by society that a 15-year-old can't vote, can't join the armed forces and cannot buy alcohol, because society has recognized that children do not have the ability to appreciate the long-term consequences of their actions," he said.
"But they can treat them as adults in court, when we have very capable remedies for them in the juvenile justice system, which is geared towards rehabilitation," Weekes added.
The attorney said he and the other two public defenders plan to make separate motions to the court asking that their clients be allowed to post bond.
Detectives say eyewitnesses told them that Mendez used a lighter to set fire to Brewer after Jarvis allegedly poured alcohol over him. They said Bent allegedly encouraged the attack.
Authorities say that Mendez admitted setting Brewer on fire, and that he made a "bad decision," according to an arrest transcript.
Two other boys who were allegedly involved -- a 13-year-old and a 15-year-old -- have been charged as juveniles.
Witnesses say Brewer jumped into the swimming pool at his apartment complex to put out the flames.
Detectives with the Broward County Sheriff's Office have been unable to interview Brewer.
"We hope that we can maybe get a statement this week," sheriff's spokesman Jim Leljedal said. "Detectives have been waiting for him to recover to the point where he's strong enough to give us a complete statement."
Doctors say Brewer is improving but his condition is tenuous because of the severity of his burns and the possibility of infections. Most of his burns are on his back and buttocks; his face and hands were largely spared, doctors say.
Brewer's doctor told CNN the teen faces several more months in the hospital, and will need multiple skin grafts and surgeries.
"They still have to perform several operations on him for skin grafting, but his parents are with him all the time," Nelson said.
"I don't tell him what happened," Brewer's mother, Valerie, told CNN affiliate WFOR-TV. "I just tell him he's in the hospital and he's safe and he's getting better.
"And he'll say, 'Am I going to be OK?' And I say 'Yes, Michael. You're going to be fine. You're going to be just fine,' " she said.
Investigators believe Brewer owed Bent $40 for a video game. When Brewer did not pay, police say, Bent stole Brewer's father's bicycle. Brewer reported him to police and Bent was arrested, police say.
The next day, the group surrounded Brewer. According to witnesses, the five boys called Brewer "a snitch" and set him on fire.
The Brewer family told WFOR that none of the families of the accused boys have tried to contact them, but that it doesn't matter.
"We can't focus on it. They'll get theirs is all we can say. I don't focus on it," Brewer's father, also named Michael, told WFOR.
If convicted, each of the three teen suspects could face up to 30 years in prison.
A court-appointed psychologist who has examined two of the five boys allegedly involved in the attack told CNN they are competent to take part in legal proceedings and assist their attorney.
"I can describe both of them as being afraid, being fearful," said Michael Brannon, a forensic psychologist, without identifying the boys. "I can describe both of them as being tearful at various times during the interview, especially when talking about the specific incident which led to the injuries of the victim."
Psychologists are often brought into cases involving teenagers and young adults to judge their mental capabilities to determine their competency to proceed. They must determine whether the alleged attackers understand the charges against them, the court proceedings and potential sentences.
Psychologists also must evaluate whether the defendants can talk about what happened and communicate effectively with defense attorneys.
"I don't think they expected to have happened, what happened," Brannon said. "It's a horrible event that occurred, but this was not their conceptualization, in my opinion, of what was going to happen."