Three relatives of Thacker, however, confronted Thacker in the courtroom and told him they thought he was lying to cover for someone else.
One aunt told Thacker he is "evil" and wished he had never been born.
Thacker testified today at a hearing where he was sentenced to 25 years in prison, with the eventual possibility of parole. The sentence was part of a plea deal with prosecutors.
Thacker, who had been charged with capital murder for the deaths of his parents Ronnie and Barbara Thacker, could have faced a sentence of life without the possibility of parole if he had been convicted at a trial.
Thacker - his hair grown long, and wearing a red striped Jefferson County Jail uniform with chains at his wrists and ankles - calmly and with little emotion testified about his heroin addiction and what happened the day he killed his parents
Thacker said he awoke that Tuesday morning. "I was going through really bad withdrawals from heroin," he said.
But Thacker said he went to school anyway and later checked out. He said his mom and dad picked him up and they all went to the grocery store and got back home after lunch.
Thacker said he was sitting on the couch thinking about his withdrawals and was mad that his parents had kicked his older brother, Luke, out of the house. "And the thought just came to my mind to kill them," he said.
Thacker said he got up from the couch, took a gun from a safe and called his mother to look at something in a closet. He said he shot her in the back of the head "execution style" when she responded. He said he then called out to his dad, who was outside cleaning a car, to say that his mother had fallen down the stairs.
When his father came into the house, Thacker said, he shot him too.
Thacker said he took his dad's wallet, which included about $500, and drove off in his brother's car.
After Thacker testified, the family's anger spilled out as several relatives stepped up near the witness box and confronted him.
"I swear to God I wish you had never been born," said Thacker's aunt, Vickie Knight, the sister of Barbara Thacker.
She told her nephew that there were only two people on Earth who loved him unconditionally and "you took them."
Knight told her nephew she hadn't seen him shed a tear during the hearing. Heroin isn't an excuse, Knight told him. "There is something evil in you, totally evil."
Drew Thacker responded to his aunt: "I've already done my crying. I can't cry no more."
Thacker's uncle, Maurice Thacker, told his nephew that he can't forgive him. "I don't know what kind of demons got into you. ... I hope they show no mercy where you are going and I hope you get the dog... beat out of you every day."
Knight and her husband both told Thacker he was lying to cover up for his brother, Luke, and asked him to tell the truth.
Assistant Jefferson County District Attorney Lane Tolbert also questioned Thacker to determine whether his brother, Luke, or anyone else may have had any involvement in the murders.
Thacker denied that his brother had anything to do with the death of his parents. "I told the truth," he said.
Thacker's brother does not face any charges.
Thacker's attorneys, Joe Basgier and Brett Bloomston, said that heroin addiction is especially difficult for someone in their teenage years. The two attorneys also said there is no evidence that Thacker's brother played any role in the deaths of their parents.
"He (Drew) has no incentive to lie or cover for anyone," Bloomston said.
In sentencing Thacker, Hobdy asked Thacker whether he was satisfied with his plea and quickly added: "You should be."
Thacker had pleaded guilty to one count of murder - for his mother - under the plea deal.
Tolbert said that if he had pleaded guilty to two murders then that would have been a capital murder charge. In a technicality, in order to get the reduced plea and sentence, he could only plead guilty to one murder. He said prosecutors offered the deal because of evidence and witness issues.
"In a case like this there is no justice," Tolbert said. "Twenty-five years is not justice for killing your mom and dad, who did nothing but love you. ... No one here is happy."