Signatures examined by the forensic document examiner for authenticity will eventually be categorized as genuine, or not genuine, if the examination leads to a definitive opinion. “Forgery” in a strict sense is a legal term and it’s use as a conclusion should probably be avoided by the questioned document examiner. Often a signature in of itself may be valid, but the manner in which it has been acquired or affixed to the document, or the sequence of events involved in its use are fraudulent. http://www.questioneddocuments.com/services-offered-by-ndl/s...

[...] he took every reasonable means to ascertain the authenticity of the signature [...] https://books.google.com/books?id=4BhDAQAAMAAJ&pg=PT615&lpg=...

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Note added at 20 mins (2016-04-06 23:08:40 GMT)
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Я думаю, что в суде не столько занимаются "поиском" автора подписи, сколько установлением, что именно данное, конкретное лицо, поставило подпись под документом. Отсюда и предложенный перевод.

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Note added at 5 days (2016-04-12 14:24:52 GMT) Post-grading
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Was happy to help.