When it comes to JFK's assassination, conspiracy theorists love to seize upon one political discrepancy: While the Warren commission concluded that JFK was shot by three bullets from a lone gunman -- Lee Harvey Oswald -- a Congressional committee 15 years later re-examined the incident and concluded that four shots were fired. One of the key pieces of evidence? A tape from a dictaphone at police headquarters. Apparently there was a live microphone on a police motorcycle near the Kennedy motorcade, and it caught the whole thing. The Congressional committee based its "four shots" theory partly on the sounds of that Dictaphone recording.

So why don't we use modern computer techniques to analyze the recording and figure this out once and for all? Because, as the New York Times explains today:

Like old 78 r.p.m. records, the Dictaphone belt became worn and damaged through constant replay for analysis using a stylus. When it became property of the National Archives in 1990, the technical staff recommended that no further efforts be made to replicate its sounds through mechanical means.

This is a rather sober lesson for our digital age. Librarians have warned us that our supposedly "indestructible" media -- DVDs, CDs, hard drives -- are rarely so. What's more, even when we still have functioning old media, we frequently lose the devices necessary to read it. (How many of you out there have a dictaphone at home? Hell, who's even got a computer with a slot for 5.25-inch floppy?) And in a lovely gloss on the Soviet dictum "destroy this message before reading it", many old forms of media can be ruined merely by the act of listening to them. Lest we think that this is limited to physical media like dictaphone tapes, it's worth noting that when you open an old Microsoft Word document -- such as something written in Word 5.0, for example -- new versions of Word will actually reformat it on the fly, subtly deranging its code. That's not a big deal for you or me, but for the courts -- which require documents be forensically pristine when you read them -- Word can be nasty little paper-shredder. Apparently that's why so many lawyers use WordPerfect instead; it does not, in contrast, reformat a document merely by opening it.

Mind you, what technology wrecks, further technology can sometimes fix. As the Times reports, scientists at Lawrence Berkeley National Laboratory are working on a device to digitally scan the contents of the dictaphone tape without perturbing it. I suspect it's something like those newfangled laser-driven record players -- in which a laser reads the vinyl grooves, so that you can play a record endlessly without eroding it the way a needle would.