Win Lawson grew up in western New York, where his father was an accountant, his mother a teacher. He worked in counterintelligence in the Army and developed an interest in law enforcement. So he applied to the Secret Service when he and his wife, Barbara, were living in Syracuse. He did so just in time: In those days, applicants could not be over 30, his age when he applied.

Prized for being a stickler for detail, he became one of the agency's most valuable "advance" men, the job he held when President Kennedy came to Texas.

It was his job to check out the host city — in this case, Dallas, where citizens had recently heckled both Vice President Lyndon Johnson and U.N. Ambassador Adlai Stevenson.

"The city was absolutely going out of its way to be cordial," said Lawson, who lives in Virginia Beach, Va.

As the motorcade left Love Field, en route to downtown Dallas, Lawson and the other agents — all of whom were in the procession — were staggered by the number of people who lined the streets, the thousands who waved and cheered.

As the motorcade began the last leg of its journey, heading down Elm, the feeling was one of triumph and vindication for Dallas.

And then came the first shot.

Like most witnesses, Win Lawson recalls two more, though puzzled by the quicker pace between the second and the third, which all but tore the president's head off.

The madness that ensued found him and other agents racing to Parkland Hospital, where he was among the first to see the president's body, crumpled in the Lincoln.

"You could see the damage to the head, which was devastating," he says. "You could see the color of the skin, which was gray, but not gray, really. I knew it had to be a fatal wound. I never saw the president alive again or his body again."

Instead, he embarked on a 40-year trial of re-examination. "I must have thought a million times, what could I have done to prevent it?" he said. "And what could I have done about 20,000 windows?"

He says he believes fervently that Oswald acted alone. Conspiracy buffs, he says, neglect to consider the 10 miles of the motorcade's route, stretching from Love Field, to Lemmon Avenue, to Turtle Creek, to Cedar Springs, to Harwood, to Main, to Elm, to history. The trip was to take 35 minutes before arriving at the Trade Mart.

"There were a million better places from which to have fired a weapon," said Lawson.

He did not let the assassination derail him. Rather than go to a field office, as most agents eventually do, he remained at Secret Service headquarters until he retired. He also chose to remain in the agency's protective division, a decision he admits was influenced by Dallas.