Perhaps the most document-specific rule of evidence concerns the often misunderstood best evidence rule, which derives from 18th century English common law. The rule states that to prove the contents of a writing, recording or photograph, the original document must be produced, provided its unavailability is not the fault of the party trying to authenticate the document's contents. If the original cannot be located, the author can validate its contents through sworn testimony. Either that, or the person who read the writing, listened to the recording or viewed the photograph may testify as to its content. However, if the best evidence isn't available, then federal and state rules of evidence usually permit the use of a mechanical, electronic or other similarly produced facsimile instead of the original.

    When a document is created digitally, certain problems in evidence arise. For example, since a digital copy of a digitally created document is a perfect clone of the original document, it is regarded as equal in evidentiary force to the real thing, provided that the copy can be properly authenticated. To most techies, this rule intuitively appears to be correct.

    There are instances, however, where the legal outcome may be counterintuitive, even to the most ardent technophile. Take, for example, an e-commerce transaction where specific goods are bought and sold at an Internet site. A common customer practice is to memorialize the transaction by creating a screenshot of it as an archived PDF document. If a dispute emerges over the transaction, the buyer is protected because s/he has documentary evidence of the purchase.

    What of the seller? If ordered to produce the best evidence from its web-based archive, chances are that the best the seller can do is reconstruct the original web transaction from a stored set of website data points based upon the buyer's identity and the time of the completed transaction. But what if the buyer's PDF version of the transaction differs from the seller's reconstruction of it - and both descriptions are certified free from fraud - who wins the dispute in court? The answer is that the buyer wins because s/he recorded the transaction as an original document when it was first memorialized, making it by definition the best evidence. Although the reconstructed version may be an accurate one based upon the available data, it will be deemed legally inferior because it differs from the seller's document and is one created after the fact through a data-driven process, rather than a document-based one.

    Hence, the seller's after-the-fact digital reconstruction cannot trump the buyer's original PDF memorialization because, for reasons already cited, the PDF document is the best evidence. Had the seller also created an authentic document at the time of the transaction - one that differed from the buyer's - then there would be a genuine controversy over the facts that a jury would have to decide.

    At present, there is no body of law that specifically controls digital documents, just as there is no set of rules called "Internet Law." Indeed, a digital document is, in actuality, a set of code-based document descriptors that materially exist as magnetic impulses on a hard drive that, when viewed with the right document authoring software, can qualify as legal evidence. Absent the authoring software, those impulses cannot qualify as a document. Likewise, they don't qualify as evidence in the courtroom, unless a surviving paper copy or a digital copy in "living" media format can be discovered and authenticated. When it comes to how the law governs the digital world, our legal system has some catching up to do.
