The end of a trial which transfixed the country came with merciful swiftness. The decision was not unexpected but might well have been clinched by a masterly final appeal from David Bruck, Ms Smith's lawyer, culminating when he read to the jurors the admonition of Jesus, "Let he that is without sin among you, let him first cast a stone at her" - from the same Bible that had been used to swear them in.
In a deeply religious community the effect was stunning, outweighing the prosecution's relentless depiction of the 23-year-old former secretary as a manipulative and evil murderess, who sent three-year-old Michael and 14-month-old Alex to their deaths in a nearby lake to keep the favour of her rich lover who threatened to leave her because of her children.
Proceedings here, from jury selection to last Saturday's verdict of first degree murder to yesterday's sentencing, lasted just 17 days - a mere eyeblink compared to the grinding O J Simpson saga in Los Angeles. But the sorrows and secret shames laid bare in wrenching detail this week have left wounds upon a small and close-knit southern town that may take years to heal.
First David Smith, who believes his former wife should die, spoke almost unbearably of his grief at losing his two sons, and how he learnt from television that his wife, who originally claimed they had been taken by a black kidnapper, had confessed to strapping them into her Mazda car and rolling them into a nearby lake.
In a final attempt to secure the death penalty (in South Carolina by lethal injection or the electric chair), prosecutor Tommy Pope showed the jury crime scene photos of the boys' tiny, bloated corpses.
But scarcely less harrowing testimony came from defence witnesses, who had watched or shared Ms Smith's miserable life, pleading that she should be spared.
"We've had everything in our lives hung out in front of the world to examine," said Tommy Vaughan, whose brother Harry - Susan's father - committed suicide when she was six. "But we love our family and we love Susan."
Beverley Russell, the local Republican party leader and Christian Coalition member who became her stepfather, testified how he had sexually molested her when she was a girl. He read from a letter he sent her last month: "You don't have all the guilt in this tragedy. My heart breaks for what I've done to you."
One after another, friends, relatives and ordinary townspeople testified how Susan Smith had been a model mother; how Michael and Alex were always immaculately turned out and cared for, how she never smacked them. A model mother that is until the October evening when, for a reason yet to be convincingly explained, she killed them.
Since her arrest nine days later, she has wanted to take her own life. "She talks about suicide, she talks about her little boys," Felicia Mungo, a guard who monitors the video from Ms Smith's maximum security cell, where she is under 24-hour suicide watch, told the court. She spends long periods kneeling, with a bible in her hand, sobbing. "She doesn't cry loudly," said Ms Mungo, "It's almost a silent cry."
Despite the atrocity of the crime, few ever expected the jury would hand down a death sentence, still less that it would be carried out.
Under South Carolina law, the 12 jurors must be unanimous in their recommendation. If even one refused, life imprisonment with no possibility of parole before 30 years was the mandatory alternative.
Statistically the odds were overwhelming she would not be put to death.
A recent Justice Department study shows that parents who kill their children tend to be treated more leniently than other murderers.
South Carolina has not executed a woman since 1947, and only one woman has been executed in America since capital punishment resumed in 1976. Of 3,009 Death Row inmates across the country, only 42 are women.