The forensic document examiner is expected at all times to be a staunch non-advocate. This may be more difficult than it seems. He is after all, performing his work within a judicial system that is dependent upon advocacy. His examination must never be biased because he is working for a prosecution orientated government crime laboratory or because he is being paid a substantial witness fee by an attorney or investigator.
This is not to say that the examiner should not be an advocate of his opinion. But this opinion, once formed, should not be taken beyond the scope of its limitations. Once shown to be an proponent of one side or the other, the examiner/expert witness no longer can maintain the aura of strict impartiality upon which the trade of any true scientist is built. Partiality, once discovered and exhibited in the courtroom, forever taints the witness and his or her testimony, lessening the impact and validity of any future examination independent of accuracy. The conservative label worn by the document examiner during the opinion forming process of the examination must be carried over to subsequent testimony.
Normally, differences in opinion testimony should be nothing more than how different Document Examiners address the gray area of probability. Perhaps one examiner “identifies” Mr. Smith as being the writer of the questioned material and the other examiner opines that Mr. Smith was “very probably” the author of the disputed document. These slight divergences in opinions occur from time to time. They are nothing more, and nothing less, than the qualitative portion of the subjective mental database of the examiner. While one examiner’s highly probable opinion may be based upon three or four years experience, the other examiner is justified in rendering an identification based upon eight or ten years experience. There will be times, however, during an examiner’s career that diametrically opposite testimony will be encountered. There may be several reasons for such opposition opinions.
Opinions that tend to occupy the opposite ends of the opinion scale may be brought about by inconsistency or differences in examination materials. While both examiners have the same questioned documents, one may have photocopies of a lesser quality, while the other has the original documents. They may have been provided entirely different sets of standards. One set of standards may be freely executed and contemporaneous with the questioned material, duplicating many of the features that occurred during the writing of the disputed document, while the other may be standard material that is not contemporaneous, may have occurred many years before, may have been written while influenced by medication, deception, or other factors. They may even be spurious in and of themselves.
However when both examiners have used the same evidence and equipment, resultant opinions should be similar or at least on the same side of the opinion scale. When this does not occur, the possibilities of ethical issues or training insufficiencies may well be the source of the error. Fortunately when this conflict occurs, other surrounding facts in the case, or perhaps third party examiners, will provide a resolution to the dispute.
The competent and ethical examiner will, during the course of a career, confront some sort of expert opposition. This conflict should serve to strengthen his own resolve and moral fiber.