Susan Smith, who drowned her two young children 30 years ago ...

COLUMBIA, S.C. — Susan Smith, the mother who shocked the nation 30 years ago when she rolled her car into a lake with her two young sons inside and watched them drown, was denied parole Wednesday.

Smith, 53, pleaded for release via a video link from prison. She needed to convince a simple majority on the seven-person panel that, after three decades behind bars, she was ready to rejoin society.

The panel voted no unanimously.

Before the parole board ruled, a weeping Smith acknowledged that what she did to 3-year-old Michael and 14-month-old Alex "was horrible."

"I would give anything if I could go back and change it," she said, taking off her glasses and wiping her eyes. "I'm sorry. I know that's not enough. I know they're just word but they come from my heart."

Smith acknowledged that she has not always been a model prisoner behind bars. But in closing, she said, "I am a Christian and I know that God has forgiven me."

When it was his turn to speak, Smith's ex-husband and the boys' father, David Smith, urged the board to deny her request for parole. He was flanked by still-grieving relatives and some members of the legal team who prosecuted Smith. All wore pins bearing the photos of the two little boys.

"It's been a tough 30 years," David Smith said, stressing that he was there to advocate on behalf of their dead sons. "This wasn't a tragic mistake ... She purposely meant to end their life."

And the time Smith has already served, it's "just not enough," he said.

"So I am asking that you please deny her parole today," David Smith said.

Smith's bid for freedom came almost 30 years to the day after she falsely claimed that she had been carjacked late at night near Union, South Carolina, by a Black man who drove off with Michael and Alex inside the car.

Her false claims garnered massive media attention and sparked a nine-day manhunt during which she and David Smith, her then-estranged husband, pleaded on national television for the boys' safe return.

"As a mother, it’s only a natural instinct to protect your children from any harm, and the hardest part of this whole ordeal is not knowing if your children are getting what they need to survive and it hurts," Smith said on NBC’s “TODAY show.

But just hours after that Nov. 3, 1994, interview, Smith confessed to killing her sons.

At her trial the next year, prosecutors argued that Smith killed them because the wealthy man she was having an affair with suggested they could not be together because he did not want children.

Her attorneys argued that she was the victim of sexual assault by her stepfather and was suffering a mental breakdown when she killed her sons.

Smith was found guilty of murder and the jury sentenced her to life in prison with the eligibility of parole after serving 30 years, although prosecutors had sought the death penalty. 

During a press conference after the hearing Wednesday, David Smith said that his ex-wife will be up for parole again in two years and he'll be there to oppose it.

"At least I know that, for now, she'll be behind bars," he said.

From her jail cell, Smith continued to claim she was a good mother. 

In a 2015 letter to The State newspaper in South Carolina, she wrote: “Something went very wrong that night. I was not myself. I was a good mother and I loved my boys... There was no motive as it was not even a planned event. I was not in my right mind… I am not the monster society thinks I am.”

Smith also has a checkered record in prison, including multiple disciplinary actions.

Her first infraction occurred in 1997 when she was caught with contraband, a razor. 

Then in 2000, Smith was moved from the Women’s Correctional Center after two prison guards pleaded guilty to having sexual encounters with her.

The following year, Smith violated rules by not standing for count and was restricted to her cell for 45 days. In 2010 and 2015, she was penalized with disciplinary detention and the loss of canteen privileges for using drugs, including marijuana, according to the South Carolina Department of Corrections. 

In arguing that she should be paroled, Smith’s attorney Tommy A. Thomas argued that she was a changed woman who survived several suicide attempts while behind bars and overcame the “stigma” surrounding mental health to get treatment for her depression.

Thomas agreed that Smith’s crime was “horrific,” but said the suicide of her father when she was 6 years old “set the stage for serious depression” that “snowballed” into tragedy. He then read a passage that Smith wrote explaining why she killed her sons.

“I knew Jesus would take better care of them than I could,” Smith wrote, according to Thomas.

But, Thomas added, while Smith deserves to be paroled, “I don’t think she will ever be able to forgive herself.”

Tommy Pope, the Republican speaker pro tem of the South Carolina House, who prosecuted Smith, adamantly disagreed. “Susan always focuses on Susan,” he said.

Juliette Arcodia reported from Columbia, S.C., Corky Siemaszko reported from New York City.

Corky Siemaszko

Corky Siemaszko is a senior reporter for NBC News Digital.