Document examination expert witness Ronald N. Morris is a certified forensic document examiner and in this excerpt from Submitting a Handwriting Case for Examination, he writes some final thoughts.
Please take the time necessary to prepare your case for submission to the laboratory. Proper preparation is essential to ensure that the examiner has the documents necessary for a meaningful examination and comparison, and that the request is clearly worded and understood. If assistance is needed before or during the preparation process, please contact the FDE for assistance.
It is extremely important to remember that if the documents being submitted are for handwriting examination, a substantial percentage of the known writing should repeat the questioned material. If possible, the collected writings should have been written around the same time as the questioned writing, and the requested writing as close to the date of the questioned writing as possible.
The known writing, while not necessarily repeating the questioned writing, should contain numerous repetitions of the same written letters and letter combinations as in the questioned writing.