as will make him feel competent to express an opinion.

He may always give the reasons for his opinion, but he must confine
his testimony to his opinion based on the handwriting itself, and not
as affected by the facts of the case. He cannot state any inferences
deduced from the facts. He must also testify himself. Evidence of what
an expert has said with reference to a writing is inadmissible for the
purpose of bringing that opinion before the court.

An expert may be tested with other papers in the case, but not with
irrelevant papers, and the whole of the test paper must be shown him.
He is entitled to see it all.

Letter-press copies and duplicates made by writing machines are not
originals and therefore cannot be used as a standard of comparison.

An expert cannot give an opinion as to the genuineness of a signature
based upon a comparison thereof with signatures not before the court.

The standard of comparison used by the expert must be produced in
court. Photographic copies are admissible when accompanied by the
originals. When original writings are in evidence and the genuineness
thereof disputed, magnified photographic copies of the writing and of
admitted genuine writings are admissible in evidence, for comparison
by jury or expert when accompanied by competent preliminary proof that
the copies are accurate in all respects except as to size and color.

The services of the expert are required in a wide range of civil and
criminal cases. Where handwriting is questioned on notes, checks,
drafts, receipts, wills, deeds, mortgages, bonds, anonymous letters,