In Checklist of Suspicious Features, Jacqueline A. Joseph, Certified Document Examiner and handwriting expert witness writes:
If you have a suspicious document or handwriting or typewriting, these clues should alert you to the need for a document examiner:
No one knows the document’s origin or the history of its custody.
The text of the document seems to anticipate and answer objections that will be raised against it, especially peculiar ones.
The materials or the literary form of the document are not what you would usually expect in such cases. For example, a will purports to be a formal one drawn up by an attorney, but the paper is ordinary bond. Another example would be a will that uses archaic terminology that contemporary attorneys no longer employ.
For more, see http://www.jjhandwriting.com/