Are there any standard techniques for comparing signatures to determine the likelihood that they are or are not by the same person?

When my great-5-grandfather Daniel Cooper signed his will in 1792, his signature looked like this:

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42 years earlier, someone named Daniel Cooper signed his name as the executor for the will of Elias Van Court. That signature looks like this:

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The two signatures are similar, but definitely not identical. The later signature is definitely "loopier" than the earlier one. My ancestor Daniel Cooper and Elias Van Court lived very close to each other, so it certainly makes sense that he would be the executor, but I don't know enough about assessing signatures to be sure either way,

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    I'm no expert, but the 2 signatures look very different to me (capital D, the a that follows it and the n. And the differences don't look like anything you'd expect to see develop by age or infirmity. – ColeValleyGirl Jun 26 at 7:57
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    The first useful link that I found was on - I shall leave a detailed reading to yourself but would agree that these are not the same writer. The 2nd seems to be made of strokes joined at angles. The first, as you say, of curved loops. That's the basic form, before you reach things like how the lower part of the D is made - though it might be that particular corner structure could change. But this is just my opinion. – AdrianB38 Jun 26 at 18:46
  • Don't forget Daniel would have been about 96 when he signed his will on 1 Feb 1791 ... No wonder he had a scribbley signature! – Phyllis Minner Nov 28 at 22:52

Are there any standard techniques for comparing signatures to determine the likelihood that they are or are not by the same person?

Yes, but they are based on comparing multiple examples. They form part of a body of techniques known as Handwriting and Signature Analysis used by forensic specialists (not to be confused with the pseudo-scientific techniques for determining personality based on handwriting, known as graphology). In the case of signatures:

"... detailed microscopic comparative examinations are made of a set of known ("specimen") signatures and one or more questioned signatures, the writer of which is in doubt."

Those techniques would not be applicable in this case. Here we have only one specimen signature, and the pair are separated by half-a-lifetime!

Many things can cause changes to our signature over time. One very famous example being the signature of Guy Fawkes before and after he was subjected to "the gentler Tortures":

Guy Fawkes' signature

While there is nothing to suggest anything so extreme in Daniels case, it must be noted that we know nothing of changes in Daniels health over he intervening 42 years. To give just one example, osteo- or rheumatoid-arthritis in his hands might have made it more difficult to hold a pen (in modern populations, between 10% and 20% of adults exhibit symptomatic osteo-arthritis by age 60. The percentage increases with age).

Conditions like these, which have a gradual onset, would have resulted in changes in his writing style, and so also to his signature.

As a result, none of the standard techniques for comparing signatures are really appropriate in this case. You would need (preferably multiple) examples of his signature from the intervening period in order to make a meaningful comparison between them.

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