That was until 3.38pm on a warm sunny day in May 1985 when, while driving home from a nearby shopping centre she stopped at the mailbox in front of the family house near Columbia, South Carolina to post a letter. At that moment, Shari Faye disappeared and was never seen alive again.
Only minutes later, her father, Robert, found her car at the top of the long driveway to the house. The door was open and the engine was running. Shari's handbag was lying on the passenger seat. But of Shari there was absolutely no sign.
After a frantic search, Robert Smith called the police. This sort of thing simply didn't happen in Columbia, a peaceful rural community which was proud to embody the very notion of family values. Sheriff Jim Metts, a former FBI agent, was a friend of Robert Smith and he instinctively knew this was no walkout after a family tiff.
Soon he had organised what was to become the biggest police manhunt in South Carolina history, assisted by over a thousand civilian volunteers. But to no avail. Shari Faye Smith had disappeared as completely as if she had stepped off the planet.
For three days the anguished Smith family waited for news. Then, that evening, came the first phone call. A man, obviously disguising his voice, claimed that he was holding Shari prisoner.
He told Robert Smith: "So you'll know this isn't a hoax. Shari had on a black and yellow bathing suit underneath her shirt and shorts," and added: "You'll get a letter later today." There was no ransom demand.
The two-page handwritten letter from Shari came by special delivery that afternoon. "Headed Last Will and Testament" it was a heartbreaking message full of love and fear and ended with the words: "I am sorry if I ever disappointed you in any way.
I only wanted to make you proud of me because I've always been proud of my family. There's so much I want to say that I should have said before now. I love you all and God bless. FBI agents Jim Wright and Ron Walker, now heading the inquiry with Sheriff Metts were deeply worried by the letter. They knew they were dealing with a sophisticated and extremely dangerous man and that Shari's life was in the balance — indeed, she could already be dead and her killer could be contemplating another similar crime.
They surmised that what probably happened was that the kidnapper had seen Shari out shopping and followed her home. Her tragedy was to have stopped at the mailbox, so allowing her abductor to pounce.
The following day there was a further call, this time taken by Shari's mother, Hilda. "Do you believe me now?" the kidnapper asked. "I need to know that Shari is well," Hilda said, to which the kidnapper replied: "You'll know in two or three days."
By now FBI experts had tapped the family's phone hoping to trace the kidnapper's calls but in 1985 "trap and trace" required keeping the caller on the line for at least 15 minutes and that was rarely possible. However a recording system had been set up so that the kidnapper's voice could be compared with other FBI voice-prints and hopefully identified.
The following evening the kidnapper called again and this time spoke to Shari's 21-year-old sister, Dawn, to whom he gave details of the kidnapping.
He had stopped his car when he saw her at the mailbox, had a friendly chat and then abducted her at gunpoint.
He was now prepared to release Shari the following day and told Dawn to have an ambulance standing by. He then gave explicit instructions to a location 20 miles away in neighbouring Saluda County.
It was there, on a wooded hillside, that police found the body of Shari Smith. She had been suffocated with duct tape over her nose and mouth. But of her killer there was no sign.
The Smith family heard nothing more until the day of Shari's funeral. Then in a call, again taken by Dawn, the killer said the abduction had got out of hand. He hadn't meant to kill Shari and now he was going to kill himself — "I'm not going to prison or the electric chair."
In the meantime, he said, he had something important to do. What that was became apparent a fortnight later when 20-year-old Rosie Helmick was abducted from the garden of her family home in Richland County, 25 miles from Columbia.
A neighbour saw a car stop and watched in horror as the driver grabbed the girl, pulled her into the car and drive off. Later that day, Shari's killer phoned Dawn Smith and gave the precise location of Rosie's body. Then he said: "God wants you to join Shari. It's just a matter of time. You can't be protected 24 hours a day..."
Faced with the new threat, police poured all their resources into hunting for the killer who had threatened to strike again.
An experimental device called an Esta machine, able to detect microscopically-slight impressions made on paper, was flown in from New York and used to examine Shari's last will and testament.
After days of work, a technician was able to detect a partial grocery list written on a sheet of paper which had been higher up the pad. It also contained a string of numbers which turned out to be the phone number of a house in Huntsville belonging to a middle-aged couple, Ellis and Sharon Sheppard.
Interviewed by police, the Sheppards were quickly dismissed as possible suspects. But had they given their number to anyone? Ellis Sheppard remembered that he had — to a man in his early 30s who recently house-sat for them for six weeks while they were on holiday. The man had written the number on a loose-leaf pad. His name was Larry Gene Bell.
Later, when police played a recording of a conversation Shari's kidnapper had had with Dawn, the Sheppards immediately identified the voice as Bell's.
Larry Gene Bell, an electrician and oddjobman, was arrested outside his parents' house in Columbia as he left for work the next morning.
While he was in custody his room was searched and his clothes subjected to examination. On a pair of blue jeans, forensic scientists found hairs that matched Shari Smith's and Rosie Helmick's.
Bell also had an extensive police record including convictions for abduction at gunpoint, for which he was jailed for seven years. Police were now convinced they had finally found their man.
Larry Gene Bell stood trial for double murder and kidnapping in January 1986 in Charleston, Berkeley County.
He didn't give evidence or admit any guilt. He spent the trial writing notes on the same pad on which Shari Smith's last letter had been written and after a month of testimony it took the jury only 47 minutes to find him guilty of all charges.
He was sentenced to death. After ten years on death row in South Carolina Central Correctional Facility, Bell finally went to the electric chair in April 1996. He never showed any remorse for what he did.
Shari's sister Dawn, Bell's next intended victim, became runner-up in the Miss America beauty contest and is now a country and gospel singer frequently seen on TV.
"I still think of Shari every day" Dawn says. "She was such a beautiful person and even in her last letter was thinking of her family rather than herself.
"Her life was so tragically short. But if I live to be a hundred I will never achieve anything like she did in terms of simple human goodness."