Derrick Charles, 32, was executed in Texas on Tuesday for the 2002 murders of his girlfriend, her mother, and her grandfather in their house.
Charles was pronounced dead at 6:36 p.m. CT, the Texas Department of Criminal Justice said.
His last statement was, "I'm ready to go home."
Update: 7 p.m. May 12: The Supreme Court denied a stay of execution to Derrick Charles on Tuesday.
Charles, then 19, was convicted of killing his 15-year-old girlfriend, Myeshia Bennett, by repeatedly dropping a television on her head, the Houston Chronicle reported. He was also convicted of beating and strangling her 77-year-old grandfather, Obie Bennett, and sexually assaulting and strangling her 44-year-old mother Brenda Bennett.
His lawyers asked the United States Supreme Court on Monday to stop his execution to provide them time and resources to present claims that Charles is too mentally incompetent for the punishment.
They claimed he "suffered from severe and debilitating mental illness since childhood" as a result of genetic inheritance and the environment in which he was raised.
In a statement to BuzzFeed News, his lawyer, Paul Mansur, said, "The State of Texas runs an unacceptably high risk of killing a person whose mental illness is so severe he cannot comprehend why he is being executed."
In 1993, Charles was diagnosed with a depressive disorder and as 10-year-old he was violent towards his peers, easily lost his temper, had witnessed domestic violence and had to undergo treatment due to "serious dysfunctionality at home and at school," according to court records. Hospital records also showed he was a risk of suicide, mental anguish and suffered seizures and stuttering as an infant. A psychological assessment noted that Charles came from a "very deprived background."
In 1995, his parents admitted him to the hospital due to his depression, lack of sleep, irritability and violent episodes – including threats and fighting at school and explosive outbursts. Hospital records of that time said Charles tested "in the intellectually deficient range of intelligence," and exhibited "some signs of neurological problems."
The state called Charles' incompetency claim "meritless" and Texas state and federal courts refused to authorize the resources his lawyers say he needs to determine his competency to be executed.
On May 8, the Fifth Circuit Court of Appeals also refused to stop Charles' execution.
Charles had previously been sentenced to three years for burglary and had been arrested several times as a juvenile. He received more than 100 write-ups and was labeled a "chronic serious offender" during his custody at the Texas Youth Commission.
Charles could become the seventh person to be executed in Texas this year. In March, the state acquired a new supply of its lethal injection drug, pentobarbital, from an unidentified licensed pharmacy according to a Texas Department of Criminal Justice (TDCJ) official. The TDCJ said it has enough pentobarbital to conduct four executions, of which one took place in April.
At the time of the crime, Charles was hiding in his 15-year-old girlfriend's house after she and her mother left for errands in July 2002. Her mother, Brenda had secured a restraining order against him which had angered him, according to court records.
When Myeisha's 77-year-old grandfather entered the house, surprising Charles, he beat him with a lamp and trophies and punched him in the face repeatedly, eventually strangling him to death with a lamp cord, according to Charles' confession to the police.
When Myeisha and Brenda returned home, Charles tied them up and gagged them with a sock. "Myeshia would tell me that she loved me, and I told her it was too late," Charles told the police in his confession. He then tried and failed to strangle her with an extension cord, after which he repeatedly hit her in the face with a car speaker. He then dropped a television set on her head a until she died.
After failing to electrocute Brenda, 44, in a bathtub, he dragged her out to the living room with an extension cord tied around her neck. "She kept asking me why I was doing this," Charles told the police. "I told her that I couldn't really tell her because I really didn't know why I was doing this." He then sexually assaulted and strangled her to death.
Charles pleaded guilty on the first day of his trial.