Fence-Jumpers Low on Scale of Security Threats

The radar on the White House roof has been upgraded to protect against kamikaze planes, Pennsylvania Avenue has been blocked to foil car bombers--and still a lone gunman can clamber over the wrought-iron fence and sprint to within 50 feet of the President’s windows.

The response from the men and women who guard the White House: Unless you want to turn the President’s house into a walled-off fortress, there just isn’t much you can do about “jumpers”--except try to stop them on the lawn.

Since 1989, at least 22 intruders have jumped over the White House fence the way Leland William Modjeski is accused of doing--an average of about four such incidents each year. None of them came close to harming the President or his family.

“It is possible to jump over the White House fence--and get arrested and apprehended and subdued,” said Ronald K. Noble, the Treasury undersecretary who oversees White House security. “But if you want someone to not jump over the fence, you’re going to have to have Secret Service officers lined up all the way along the edge of the complex. . . . Or an electric fence. Or a huge wall 30 feet high.”

Instead, Noble and other officials say, the greater dangers to a President come from two other sources: his ventures into crowds in the world outside the White House grounds, and the specter that a determined terrorist might use high explosives or other sophisticated weapons to penetrate the building’s defenses.

In every case, the President and his advisers must grapple with the same dilemma: how to protect the chief executive in a violent time without sealing him off from other citizens.

“As long as you have what appears to be an open White House complex,” Noble said in an interview, “you have to have measures that aren’t as visible” as fences or walls. Those include the silent electronic alarms hidden on the grounds that Modjeski touched off as he ran toward the mansion’s southeast corner.

And the uniformed guards don’t feel free to shoot anyone who comes over the fence, a senior official noted. “We have fence-jumpers throughout the year who jump for pranks,” he said. “We have people who jump over the fence just to use the bathroom. . . . So the Secret Service does not simply shoot someone who has jumped over the fence unless there are other indications of danger.”

President Clinton may not actually have suffered more attacks than his immediate predecessors; the White House logged a record seven fence-jumping incidents in 1991 under President George Bush, and both Ronald Reagan and Gerald R. Ford survived assassination attempts.

But Clinton has attracted a greater variety of strange assaults. In 1994, a Maryland man crashed a small airplane into the ground floor of the White House. Also last year, Francisco Martin Duran stood on Pennsylvania Avenue and fired an assault rifle at the building 29 times; two months later an apparent drive-by shooting occurred.

Officials and experts say they cannot easily explain the strange proliferation of incidents--except to note that Clinton arouses passionate feelings, and to worry that each assault may inspire another.

Officials don’t like to talk about it, but last month’s bombing of the federal building in Oklahoma City--and the harsh debate that ensued over the role of extreme-right militias--pointed to a threat more frightening than any fence-jumper: the possibility that a “copycat” bomb could be driven up to the White House fence.

That worry led directly to Clinton’s decision to approve the blocking of Pennsylvania Avenue last weekend, only 24 hours after a Treasury Department review board formally recommended the move.

“We found we couldn’t do it any other way,” said former Treasury Secretary William T. Coleman Jr., a member of the panel. “We asked if you could ban trucks and let cars through, and we found out that a Lincoln Continental or a Cadillac could carry something that would be a problem too.”

The panel’s 11 recommendations--including five that have remained classified--also covered new ways to detect intruders and better radar monitoring of the airspace around the White House.

One of the secret subjects was the threat that high-tech weapons such as portable, precision-guided missiles might pose to a President inside the White House grounds.

“We could not put the details in our public report, but we surveyed that,” Coleman said. “The technology we are using now is very up to date, and four times a year the top scientific people will review everything to make sure we stay up to date.”

“True terrorists, with training and direction, don’t climb the fence into the White House grounds,” said Robert Kupperman, a terrorism expert at the Center for Strategic and International Studies. “It’s all too easy for a professional terrorist to choose a more unusual, more effective route . . . including high-tech weapons.

“The most important thing that has happened is that a line has been crossed” since the Oklahoma City bombing, he added. “Terrorism is changing qualitatively. . . . With paramilitary groups and cults, terrorism has come to the United States.”

That change could prompt Clinton to make one other change: altering his own habits to spend less time mingling with crowds.

Clinton has long worried the Secret Service--and some of his own advisers--by plunging into crowds at public events and jogging on public streets and parks.

Early in his presidency, he bowed to their pressure and had a small jogging track built, with privately donated funds, inside the White House grounds.

But he didn’t like it and rarely uses it.

Instead, Clinton often runs on Washington streets or on parkland trails, accompanied by grimly jogging Secret Service agents.