Ian's message gave a summary that's in my accord with how courts work.  Since
lawyers learn by example - and the law grow by and example - here's a case
that I think closely parallels the legal issues in repudiation of digital
signature cases.  The case, which if I remember right (from hearing about it
20 years ago from a friend in law school) is known informally as the
Green Giant Peas case, and forms one of the bases of modern tort liability.

The beginning of the 20th century lead to the first mass production, distri-
bution, and marketing of foods.  Before that, you bought "peas".  Now, you
could buy a can of "Green Giant Peas", sold by a large manufacturer who sold
through stores all over the place, and advertised for your business.

Someone bought a can of Green Giant Peas at a local store.  The can contained
metal shavings.  The purchaser we injured, and sued Green Giant.  One of the
defenses Green Giant raised was:  Just because it says Green Giant on the label
doesn't *prove* Green Giant actually packed the stuff!  The plaintiff must
first prove that these peas really were packed by Green Giant.  Such defenses
had worked in the past - there are many of the same general flavor, insisting
that no recovery should be possible unless plaintiff could reach a level of
proof that was inherently unreachable.  In this case, the courts finally
threw out this defense.  I can't find the actual case on line, but at
http://www.lawspirit.com/legalenglish/handbook/evid08.htm (a curious site -
it seems to be mainly in Chinese) the following text appears:

        D. Self-authentication: A few types of documents are
        "self-authenticating," because they are so likely to be what they
        seem, that no testimony or other evidence of their genuineness need be
        produced. [474 - 475]

                1. State provisions: Under most state statutes, the following
                are self-authenticating: (1) deeds and other instruments that
                are notarized; (2) certified copies of public records (e.g., a
                certified copy of a death certificate); and (3) books of
                statutes which appear to be printed by a government body
                (e.g., a statute book appearing to be from a sister state or
                foreign country).

                2. Federal Rules: FRE 902 recognizes the above three classes,
                and also adds: (1) all "official publications" (not just
                statutes); (2) newspapers or periodicals; and (3) labels,
                signs, or other inscriptions indicating "ownership, control,
                or origin" (e.g., a can of peas bearing the label "Green Giant
                Co." is self-authenticating as having been produced by Green
                Giant Co.).

"Self-authenticating" here seems very close in concept to what we are trying
to accomplish with digital signatures - and the Green Giant example shows how
the law grows to encompass new kinds of objects.  But it's also important to
look at how "self-authentication" is actually implemented.  Nothing here is
absolute.  What we have is a shift of the burden of proof.  In general, to
introduce a document as evidence, the introducer has to provide some
proof that the document is what it purports to be.  No such proof is
required for self-authenticating documents.  Instead, the burden shifts to
the opposing console to offer proof that the document is *not* what it
purports to be.  This is as far as the courts will ever be willing to go.

                                                        -- Jerry

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