Federal Rule 702, which governs when expert testimony is appropriate, does not require that the matter under consideration be beyond lay comprehension. It states that if the expert's opinion 'will assist the trier of fact to understand the evidence or to determine a fact in issue,' the expert testimony is appropriate. Trial judges now admit expert testimony that, before the enactment of the new evidence codes, would have been rebuffed by the courts as an invasion of the jury's province. Precodification law required that an expert's opinion be based upon one or both of two possible sources of information: the expert's firsthand observations and the facts made known to the expert in court. Rule 703 endorses these traditional foundations but also provides that an expert may base an opinion on facts presented to the expert before trial. It further states that 'if of a type reasonably relied upon by experts in the particular field ..., the facts or data need not be admissible in evidence.' As recently as a decade ago, many jurisdictions required that every essential basis for an expert's opinion had to be specified during the direct examination before the opinion could be given. Federal Rule 705 abolishes this requirement. It requires only that direct examination inquire about the expert's qualifications, whether the expert has an opinion on a case-related issue, and the substance of the opinion. Overall, there is a growing tendency to admit expert testimony, leaving exposure of its weaknesses to cross-examination and rebuttal testimony.