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I'm not referring to determining personality from handwriting, I'm talking about whether a document was forged or created by a certain person by comparing handwriting on a document to a sample source of handwriting.

Catherine Holloway
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    Considered legitimate by who? Courts? (in what jurisdictions)? And are you asking if handwriting samples alone are enough for proof (i.e. to convict someone), or if they are considered legitimate along with other evidence? – Flimzy Nov 02 '11 at 23:53

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The short answer is yes. The paper titled PROFICIENCY OF PROFESSIONAL DOCUMENT EXAMINERS IN WRITER IDENTIFICATION deals with this subject directly. It was written in the lab I worked in as an undergrad and did research in a related paper that may or may not end up being published (I hope it does, but these things take a lot of time).

To quote some of the abstract:

A comprehensive writer identification test was designed and administered to a group of professional document examiners and a control group of nonprofessionals.

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Professional document examiners from the FBI performed significantly better than control group members, indicating that handwriting identification expertise exists.

The above paper I can only find an abstract for, but you have to pay to read the full thing.

A more recent paper (by the same leading author) of which I can find the full paper available, written in 1997 is titled Writer Identification by Professional Document Examiners. This paper tried a similar approach, but instead of testing between "experts" and "laypeople" they tested between experts and "trainees" and showed how different the results turned out (the experts scored a great deal better).

We report on a comprehensive test administered to more than 100 professional document examiners, intended to close this data gap in the area of writer identification. Each examiner made 144 pair-wise comparisons of freely-created original handwritten documents.

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Examination of the data and statistical tests show that the answers collected from the professional and nonprofessional groups came from different populations. The trainees’ data were shown to have come from a population that is distinct from both professional and nonprofessional groups. Unlike the professional examiners, the nonprofessionals tended to grossly over-associate. They erroneously “matched” many documents that were created by different writers, mismatching almost six times as many unknown documents to database documents as the professionals did (38.3% vs. 6.5% of the documents).

The results of our test lay to rest the debate over whether or not professional document examiners possess writer-identification skills absent in the general population. They do.

-Asaf

Asaf
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  • but incomplete. It shows the FBI probably uses handwriting as a means of matching documents to see if they originated from the same author, it doesn't show whether those techniques have any legal standing or are merely a tool used to select potential candidate documents for further analysis. – jwenting Nov 03 '11 at 07:56
  • The fact that the professionals are better than lay people doesn't prove that the professionals are good enough to make those judgments in real world situations. – Christian Nov 08 '11 at 14:16
  • @Christian and how exactly would you go about proving that they are? Just to be clear, the comparison is used as a control group. That's the point of comparing them to lay-people. Also I'm going to edit this question soon, there's discussions/law papers on how to handle this in the law. I'll try and get to it soon. – Asaf Nov 08 '11 at 14:21
  • @Asaf: It would be good to have a ROC-plot on how those professionals perform on the kind of task that those professionals are asked to perform in real life. – Christian Nov 08 '11 at 14:35