When former President Richard M. Nixon waved his famous, awkward goodbye from the door of the presidential helicopter Marine One and left the White House in disgrace 35 years ago, he also left behind an enduring mystery.
It surrounds a June conversation between the president and his chief of staff three days after the infamous 1972 break-in at the Democratic National Committee's offices in the Watergate complex in Washington, D.C. The discussion between Nixon and H.R. "Bob" Haldeman was captured by the president's secret White House recording system, except for an 18 1/2-minute gap where the tape was later erased.
Efforts to electronically salvage the lost audio from the actual tape have not worked in the past, leaving historians to rely on Haldeman's normally detailed handwritten notes for clues about what he and Nixon talked about.
But amateur historian Phil Mellinger, who spent five years constructing an elaborate Watergate timeline, believes a large chunk of Haldeman's notes taken during that 18 1/2 minutes are missing. Now, he's proposing a high-tech way to make the few pages that do still exist give up their scandal-cloaked secrets.
"I've always been doing high-tech investigations of one type or another," said Mellinger, whose intelligence career has taken him from the Air Force and National Security Agency to the private sector.
He is now the chief technology officer for Turiss LLC, a Virginia-based company that develops software and strategies to fight cyber and financial fraud. "Haldeman," Mellinger said, "destroyed the first 17 minutes of his notes and left the conclusion of his notes, which was not incriminating."
Mellinger's unique proposal was first reported by Mother Jones, which detailed the amateur historian's 'eureka' moment in late July.
The two remaining pages of notes from the meeting -- written by Haldeman on yellow, lined pads -- are stored at the National Archives facility in College Park, Md. Mellinger, who has examined the documents, says there are faint impressions on the pages, made by a ballpoint pen writing on the pages above them.
Those indentations, Mellinger believes, could be deciphered with a forensic technique called electrostatic detection analysis.
Forensic experts say it has been used to examine countless documents since being developed in the early 1980s by a British company.
"It's been a godsend," said Albert Lyter, president and chief scientific officer of North Carolina-based Federal Forensic Associates. "We use it routinely for things like bank robbery notes. You might find a grocery list embedded on a bank robbery note or, if you're lucky, somebody's name and address. It's been really useful."
It works by placing the original document under a thin plastic film. An electrostatic charge is applied to the page and then, tiny glass beads and black copier toner are cascaded or carefully brushed over the document.
"What happens is the black particles will congregate in the areas where the indented impressions are," Lyter said. "So you can actually read the writing that's there."
It's not clear that Haldeman's notes, now more than three decades old, would reveal anything. Experts say it depends on the environmental conditions at the time the notes were written and the conditions under which they've been stored since then.
"You might not find as much in a sheet of paper that old or that might have been exposed to up and down humidity for that amount of time," Lyter said. "There's no guarantee you're going to find everything that's there."
The National Archives is apparently taking Mellinger's proposal to decipher missing parts of Haldeman's notes seriously. But officials with the archives -- a taxpayer-funded arm of the federal government -- are saying little about it, beyond a recent published report.
In a July 28 online article, archivist David Paynter was quoted in "Mother Jones," saying "the reason we are going forward with this is that we've already tried with the tape itself. Here's another avenue to shed light on an important episode in history. It's very exciting."
Denying a request to interview Paynter, the National Archives said in a statement, "From time to time, individuals suggest new technologies to unlock historical mysteries. Senior officials at the National Archives are meeting to evaluate this idea."
When contacted to follow up on the statement, spokeswoman Miriam Kleiman declined to comment, abruptly hanging up the phone.
Paynter referred all questions back to the public affairs office.
Until the National Archives decides whether it will examine Haldeman's notes using electrostatic detection, professional historians and amateurs like Mellinger will continue to speculate on the 18 1/2-minute gap.
"I do it just for the love of the whole thing," Mellinger said of his Watergate obsession. "And once you actually get results, it's very addicting."
For now, the conversation between Nixon -- who would become the first U.S. president in history to resign from office -- and one of his closest aides is still a puzzle.
"People love a mystery," presidential historian Richard Norton Smith said. "We're still debating the Lindbergh kidnapping. We're still arguing over Amelia Earhart and Jimmy Hoffa. So it's not surprising that the 18 1/2 gap should be subject to renewed debate."