HUNTSVILLE, Texas -- Convicted killer Preston Hughes III proclaimed his innocence as he was executed Thursday for the fatal stabbing of a 3-year-old Texas boy and the child's teenage cousin who uttered her attacker's first name to police in her dying breaths.

Hughes long had contended he wasn't responsible for the slayings of Shandra Charles, 15, and her cousin Marcell Taylor 24 years ago in Houston, and that police had planted evidence and coerced his confessions.

The condemned prisoner's mother sobbed and wailed as she witnessed the lethal injection. Hughes' sister was at her side.

"You know I'm innocent and I love you both," Hughes, 46, said as his mother cried loudly. "Please continue to fight for my innocence even though I'm gone.

"Give everybody my love."

He took several deep breaths and then stopped moving. His mother, seated in a chair near the death chamber window, cried out: "My baby ... I haven't touched my child in 23 years."

She became more composed in the minutes after it was apparent he was unconscious.

Hughes was pronounced dead at 7:52 p.m. CST, 15 minutes after the lethal drug began flowing into his arms. No one representing his victims witnessed the punishment.

Hughes became the 15th Texas prisoner executed this year and the second in as many nights. On Wednesday, Ramon Hernandez, 41, was executed for the rape, robbery and murder of a San Antonio woman abducted from a bus stop in 2001.

The September 1988 attack on the young cousins Hughes was convicted of killing happened in a field behind a Houston apartment complex where Hughes lived. A man walking along a trail found Charles and called police. Officers found her 3-year-old cousin already dead from a stab wound that passed completely through his neck.

Charles was still alive but severely injured with knife wounds to her neck and chest, police said. When an officer asked who was responsible for the attack, she gave a name, "Preston," and said he tried to rape her. She died moments later.

Authorities went to the nearby apartments and found Hughes, the only resident with the first name of Preston. He already was on probation for a conviction of sexual assault on a child and denied any role in the stabbings.

Hughes' execution came after he lost multiple appeals in courts to block it. Two of them – filed by attorney Patrick McCann, who Hughes unsuccessfully sought to fire – failed at the U.S. Supreme Court.

Other court actions were filed on the inmate's behalf by a death penalty opponent in Houston. They were denied in the courts or could not halt the punishment, attorneys said. One of them, seeking a retesting of DNA evidence that tied Hughes to the slayings, delayed his execution for more than an hour before it was rejected by the Texas Court of Criminal Appeals.

In one Supreme Court appeal, McCann said instructions to jurors deciding Hughes' punishment were not adequate. In another, the attorney contended new evidence showed Hughes was sexually abused as a child and a jury should be allowed to consider that at a new punishment trial.

Ellis McCullough, one of Hughes' trial lawyers, said this week he was convinced no evidence was planted or mishandled.

He said Hughes, brought to a police station for interviews in the early morning hours after the slayings, made phone calls from the police interrogation room to acquaintances, including his probation officer, that "were pretty devastating taken as a whole."

Evidence examined for DNA testing after his conviction and at his request found traces of Charles' blood on Hughes' clothing. At his trial, prosecutors showed Charles' glasses were found on a couch in his apartment. Hughes, who knew Charles through a friend, said police took the evidence from the crime scene, planted it in his apartment, illegally searched the place, coerced his confessions and copied his signature to them from another document.

"The fact is I didn't kill anyone," he told The Associated Press last month, speaking from a small visiting cage outside death row.

Hughes also denied the sexual assault conviction that resulted in his probation.

"I didn't know she was 13 at the time," he told the AP of the victim in that case. "I was led to believe she was 17."

Hughes moved to Houston in 1983 from his native Buffalo, N.Y., where a rape charge against him was dismissed when the victim failed to appear in court.

He testified at his capital murder trial that he pulled a knife on "a guy who came up to me from behind" and "stuck him twice" but denied it was the 3-year-old boy or Charles.

"I didn't stab anybody," he said. "Stabbing and stuck is two different things."

Also on HuffPost:

Loading Slideshow...
  • Walter Lee Williams

    Walter Lee Williams, a former professor at the University of Southern California, was wanted for the alleged sexual exploitation of children and traveling abroad for the purpose of engaging in illicit sexual acts with children. Williams was captured June 18, 2013 in the Mexican resort town of Playa del Carmen.

  • Jose Manuel Garcia Guevara

    Jose Manuel Garcia Guevara allegedly murdered a 26-year-old woman in the presence of her four-year-old stepson in Lake Charles, Louisiana, in 2008. Guevara and the victim lived in the same mobile home park. Guevara allegedly broke into the victim's home, raped her, and brutally stabbed her to death. Guevara is believed to be in Mexico, but may have traveled to the United States using fraudulent documentation.

  • Fidel Urbina

    Fidel Urbina, 37, is wanted for the 1999 sexual assault and murder of one woman in Chicago and the 1998 sexual assault and beating of another. There have been reported sightings of him in Mexico.

  • Jason Derek Brown

    Jason Derek Brown is wanted for murder and armed robbery in Phoenix, Arizona. During November of 2004, Brown allegedly shot and killed an armored car guard outside a movie theater and then fled with the money. Brown speaks fluent French and has a Masters Degree in International Business. He is an avid golfer, snowboarder, skier, and dirt biker. Brown enjoys being the center of attention and has been known to frequent nightclubs where he enjoys showing off his high-priced vehicles, boats, and other toys. He has been described as possibly having bisexual tendencies.

  • Glen Stewart Godwin

    Glen Stewart Godwin escaped from California's Folsom State Prison in 1987, where he was serving a lengthy sentence for murder. Godwin allegedly murdered a fellow inmate in a Mexican prison, where he was serving time for a drug trafficking conviction.

  • Robert William Fisher

    Robert William Fisher is wanted for allegedly killing his wife and two young children and then blowing up their home in Scottsdale, Arizona in April 2001.

  • Semion Mogilevich

    Semion Mogilevich allegedly participated in a multi-million dollar scheme to defraud thousands of investors between 1993 and 1998. After the scheme collapses in 1998, and thousands of investors lost more than $150 million, Mogilevich -- who allegedly funded and authorized the con -- was indicted in April 2003.

  • Eduardo Ravelo

    Eduardo Ravelo was indicted in Texas in 2008 for involvement in racketeering, conspiracy to launder monetary instruments, and conspiracy to possess heroin, cocaine and marijuana with the intention to distribute. His alleged criminal activities began in 2003.

  • Alexis Flores

    Alexis Flores was allegedly involved in the kidnapping and murder of a 5-year-old girl in Philadelphia. The girl was reported missing in July of 2000 and found strangled to death in a nearby apartment in August of 2000.

  • Victor Manuel Gerena

    Victor Manuel Gerena is wanted for his alleged connection to an armed robbery of approximately $7 million from a security company in Connecticut in 1983. He allegedly held two security employees at gunpoint, then handcuffed, bound and injected them with an unknown substance to further disable them.