We'll probably never know the full truth of the Watergate crimes, because Nixon's men erased part of the audio evidence. What we do have are their notes—a trail that's run cold, even with advanced hyperspectral digging.
The NYT reports that an attempt to discover evidence of doctoring in notes written by Nixon's Chief of Staff have turned up more or less nothing, even with the use of sophisticated "video spectral comparison, electrostatic detection analysis and handwriting comparison." Will we ever be able to prove foul play? Probably not! "Since the two participants, [Chief of Staff] Haldeman and Mr. Nixon, are dead and nothing was brought up with any witnesses questioned in the only legal forum on the 18 ½-minute gap, we will probably never know," explains one of the hyperspectral researchers. Oh well. [NYT]