12. Evidence
agency rules
Many agencies have issued elaborate rules concerning how evidence should be handled, especially in a formal adjudication.  The lawyer should be fully aware of these rules.  They will prescribe, for example, how copies of original documents should be handled, questions of admissibility, introduction of business or other records, and many other matters.
Cross examination, credibility
Cross examination is commonly considered to be an effective way to determine whether the witness is testifying truthfully or less than fully truthfully.  However, cross examination is more effective on some matters than on others.  Using Davis' description, cross examination of legislative facts is less likely to be useful than cross examination of adjudicative facts. Legislative facts tend to be of a general, conclusory nature, while adjudicative facts are about specific elements in individual situations.  Expert witnesses are less likely to be undermined than lay witnesses, because the expert is often used to the cross examination experience and because the expert may have a base of knowledge about a subject that is greater than the lawyers.  In addition, there are numerous exceptions to the hearsay rule which make evidence admissible without reliance on cross examination.
A critical element in many hearing processes is who the decisionmaker chooses to believe.  In a hearing in which other factors are essentially in balance, the winner will be determined by which side is the most credible.  One type of credibility is determined by the demeanor of the witness, whether the witness gave the overall appearance of speaking the truth.  Another type of credibility is determined by comparing the statements of several witness to determine, among other things, consistency.  The credibility determination should be distinguished from the inferences drawn from the demeanor or statements.  Only a first hand observer, usually the ALJ, can measure actual demeanor.  The agency is able to draw its own inferences from the finding of credibility.  Courts sometimes distinguish issues of veracity from issues that solely involve, for example, the professional disagreement that may exist between doctor witnesses.
evaluation of evidence
Evidence may consist, in part, of matters that are within the experience of common persons or it may involve highly technical matters.  The agency is generally considered to be an expert in its area.  Courts may recognize that the agency has the expertise to interpret the evidence that the generalist court does not have.  Under this circumstance, the court may be highly deferential toward the agency evaluation of the evidence.  This deference may be particularly noticeable where there is scientific uncertainty and the agency must make a judgment call in its decision. While the court may be willing to concede such issues to the agency, it may do so only if the agency provides adequate findings to support its choice.  An agency is entitled to evaluate and interpret the evidence in the record in an adjudication.  However, it cannot use its expertise to add facts to the record by way of evaluation after the record has been closed in a formal adjudication.
ex parte communication
Evidence that is received without notice to the other side cannot be used in a closed record decisional process.  In an adjudication, the APA requires the agency to base its decision solely upon the evidence in the record and not upon evidence that may have been provided in an ex parte communication.  In rulemaking, ex parte contacts will be permitted.
explanation
The agency will be required to explain its use of the evidence.  In a formal adjudication, the explanation will be in the form of findings.  In rulemaking, the explanation will be in the form of a basis and purpose statement if the APA so requires.  In a due process hearing, findings may be required but not the formal type of findings required in the adjudication process.  Where strong and compelling evidence is rejected by the agency, the courts may require that the agency decisionmaker explain in findings as to why the evidence was rejected.  Where there is evidence on only one side of an issue and the agency seeks to ignore that uncontradicted evidence, the agency may have to meet a very high standard of explanation.
hearsay
Hearsay evidence carries the connotation of being less trustworthy than evidence presented by a witness who is subject to cross examination.  Hearsay is of greatest concern in formal adjudication where there may be a right to cross examination.  However, hearsay is admissible and can be relied upon as the sole basis for an agency decision.  It is usually defined, in part, as evidence that would be relied upon by a reasonably prudent person.  To show such reliance, it may necessary to identify what factors would lead to such reliance.  It is also important to understand that the question of admission of evidence is different from the question of what weight the decider will give the evidence.  There are many exceptions that would permit hearsay evidence to be admitted into a judicial court proceeding and if they were needed, they would also apply at the agency level.  For example, business records including computer printouts can usually be demonstrated to be sufficiently reliable for admission purposes without cross examination of all of the persons involved in producing them.  Where cross examination is not used, the opposing party should be given an opportunity to submit rebutting evidence in formal adjudication.
legislative v. adjudicative facts
Administrative law authority Professor Davis divides facts into legislative facts and adjudicative facts.  Legislative facts are of a broad nature, often involving opinion or the exercise of judgment to identify.  Adjudicative facts are specific facts about specific persons or corporations.  This distinction is a useful one to use in looking at evidence in agency decisionmaking.  It helps, for example, to determine whether the denial of cross examination is prejudicial error in a given circumstance.  Prejudice is more likely to arise if it involves adjudicative facts, and less likely if it involves legislative facts.  The legislative fact is not really subject to the same degree of verification as the adjudicative fact.
official notice
Official notice is a method of adding evidence to the record without introducing the actual evidence.  Official notice is similar to judicial notice, except that it covers more types of evidence.  Evidence is sometimes said to be subject to official notice if it is readily verifiable. Once evidence meets the test of being subject to official notice, the APA requires the other side to be given an opportunity to rebut.  Legislative and not adjudicative facts are more likely to be subject to official notice.  In this process of using evidence that has not been introduced as such, it is important to distinguish between the process of adding facts to the record and interpreting facts that are already in the record.  The addition of facts requires notice, the interpretation of facts already in the record does not require notice.
rebuttal evidence
Rebuttal is the process of putting evidence into the record to challenge evidence that is already there.  In the absence of cross examination, rebuttal evidence should always be permitted. Rebuttal is appropriate, for example, where official notice has been taken and where cross examination has been denied.  Denial of the right to rebut may be prejudicial error in these circumstances.
trade secrets
Trade secrets may be given special treatment in the agency hearing.  The holder of the trade secret may be protected against having to reveal any aspect of it.  If the material is introduced into evidence, the number of persons having access to it may be greatly limited in order to diminish the chances of losing its protected nature.