Question: What are “Learned Treatises” and are they admissible in court?
Answer: Yes, they are admissible in order to test the learning of a witness who testifies as an expert, to refer to “Learned Treatises” or books of approved authority upon the subjects under investigation. Indiana adheres to the majority view that such learned treatises are not admissible as independent evidence. An expert may rely on hearsay when they use other experts and authoritative sources of information like treatises to aid in rendering their opinions. Hearsay information customarily relied on by experts in the practice of their professions may be relied upon as a legitimate accumulation of that expert’s knowledge. In a broad sense almost all expert opinion about scientific propositions embodies hearsay indirectly. Whenever an expert testifies, they implicitly draw on such material as lectures they have heard and textbooks read during their education. For example, the opinion of a witness may be tested by a cross-examining counsel by reading from medical books. Medical books may be read to the jury, not for the purpose of proving the substantial facts therein stated, but to discredit the testimony of experts who refer to books as authority for or in support of their opinions.
