Facts on which an expert bases an opinion can be learned by the expert either at a hearing or before a hearing. The expert can rely on hearsay if the hearsay is of a type "reasonably relied upon by experts in the particular field in forming opinions." [FRE 703].

Hearsay

Hearsay is a statement or conduct made by a declarant other than while testifying, which is offered "to prove the truth of the matter asserted." [FRE 801(c)].

Some things are not hearsay, such as testimony of a witness at a prior trial when the right of cross-examination existed. Admission of testimony by the opposing party is not hearsay; however, it must be:

• The party's own statement.
• Assertively based on truth.
• Made by a person authorized to make such statements.
• Made by a party's agent or employee.
• Made by a co-conspirator in furtherance of the conspiracy.

[FRE 801(d)].