Evidence Legal Terms Glossary
Evidence terms for admissibility, burdens of proof, and courtroom practice.
Definitions
Hearsay
Hearsay is an out-of-court statement offered to prove the truth of the matter asserted. Under Federal Rule of Evidence 801, a statement is hearsay if (1) it was made outside the current proceeding and (2) it is offered to prove that what the declarant said is true. Hearsay is generally inadmissible under FRE 802 because the declarant was not under oath, subject to cross-examination, or observed by the trier of fact. However, numerous exceptions and exclusions exist under FRE 803, 804, and 807.
Hearsay Exceptions
Hearsay exceptions are categories of out-of-court statements that are admissible despite the hearsay rule because they carry sufficient guarantees of reliability. FRE 803 provides exceptions available regardless of the declarant's availability (e.g., present sense impression, excited utterance, then-existing mental or physical condition, business records, public records). FRE 804 provides exceptions available only when the declarant is unavailable (e.g., dying declarations, former testimony, statements against interest). FRE 807 is the residual exception for statements with equivalent guarantees of trustworthiness.
Relevance
Relevance under Federal Rule of Evidence 401 means that the evidence has any tendency to make a fact of consequence more or less probable than it would be without the evidence. The threshold is very low — evidence need only have some probative value. Under FRE 402, relevant evidence is generally admissible. However, FRE 403 allows a court to exclude relevant evidence if its probative value is substantially outweighed by the danger of unfair prejudice, confusion of the issues, misleading the jury, undue delay, or cumulative evidence.
Character Evidence
Character evidence relates to a person's general disposition or propensity to act in a certain way. Under FRE 404(a), evidence of a person's character is generally inadmissible to prove that they acted in conformity with that character on a particular occasion (the propensity rule). Exceptions exist in criminal cases: the accused may introduce pertinent character evidence, and the prosecution may rebut it. FRE 404(b) allows evidence of prior bad acts for non-character purposes — MIMIC (motive, intent, mistake/absence, identity, common plan).
Privilege
An evidentiary privilege is a rule that protects certain confidential communications from compelled disclosure in legal proceedings. Privileges serve policies external to the truth-seeking function of litigation, such as fostering open communication in important relationships. The most well-established privileges include attorney-client privilege, spousal privilege (both testimonial and communications), doctor-patient privilege, clergy-penitent privilege, and the psychotherapist-patient privilege. Privileges are narrowly construed because they exclude relevant evidence.
Attorney-Client Privilege
The attorney-client privilege protects confidential communications between a client and their attorney made for the purpose of obtaining legal advice. It is the oldest privilege recognized at common law. The privilege belongs to the client, who can waive it. For the privilege to apply, the communication must be made in confidence, between a client and a licensed attorney (or their agent), for the purpose of seeking or providing legal advice. The crime-fraud exception overrides the privilege when the client seeks legal advice to further a crime or fraud.
Work Product Doctrine
The work product doctrine, established in Hickman v. Taylor and codified in Federal Rule of Civil Procedure 26(b)(3), protects materials prepared by or for a party in anticipation of litigation from discovery. Ordinary work product (factual material) may be discovered upon a showing of substantial need and inability to obtain the equivalent without undue hardship. Opinion work product (an attorney's mental impressions, conclusions, and legal theories) receives near-absolute protection. The doctrine promotes thorough trial preparation by protecting an attorney's analytical process.
Best Evidence Rule
The best evidence rule (original document rule) under Federal Rule of Evidence 1002 requires that when the content of a writing, recording, or photograph is at issue, the original document must be produced unless it is shown to be unavailable through no fault of the proponent. FRE 1003 allows duplicates to the same extent as originals unless there is a genuine question about the original's authenticity. The rule prevents inaccurate transmission of critical documentary evidence and applies only when the content of the document is directly at issue.
Parol Evidence (Evidence Context)
In the evidence context, the parol evidence rule is a substantive rule of contract law that operates as an evidentiary bar, preventing the introduction of prior or contemporaneous oral or written agreements to contradict a fully integrated written contract. While sometimes discussed in evidence courses, it is technically a rule of substantive law rather than a rule of evidence. Courts evaluate whether the writing was intended as a complete and final expression of the agreement (integration) before applying the rule.
Expert Witness
An expert witness is a person qualified by knowledge, skill, experience, training, or education to testify in the form of an opinion on matters beyond the understanding of a layperson. Under Federal Rule of Evidence 702 and Daubert v. Merrell Dow Pharmaceuticals, the trial judge acts as a gatekeeper, ensuring expert testimony is based on sufficient facts, is the product of reliable principles and methods, and the expert has reliably applied those methods to the facts. Kumho Tire extended Daubert's gatekeeping function to all expert testimony, not just scientific evidence.
Lay Witness
A lay witness testifies based on personal knowledge and perception rather than specialized expertise. Under Federal Rule of Evidence 701, a lay witness may offer opinion testimony only if it is rationally based on their perception, helpful to determining a fact in issue, and not based on scientific, technical, or specialized knowledge within the scope of Rule 702 (expert testimony). Common examples include opinions on speed, sobriety, handwriting identification, and emotional state.
Impeachment
Impeachment is the process of attacking a witness's credibility. Under the Federal Rules of Evidence, a witness may be impeached by showing bias, prior inconsistent statements (FRE 613), character for untruthfulness (FRE 608), prior felony convictions (FRE 609), contradictory evidence, or defects in perception or memory. A party may impeach its own witness under FRE 607. Impeachment evidence is generally admissible only to attack credibility, not as substantive proof, though prior inconsistent statements made under oath may be substantive evidence under FRE 801(d)(1)(A).
Authentication
Authentication under Federal Rule of Evidence 901 requires the proponent of evidence to produce evidence sufficient to support a finding that the item is what the proponent claims it is. This is a low threshold — the proponent need only make a prima facie showing. Methods of authentication include testimony of a witness with knowledge, expert comparison, distinctive characteristics, voice identification, and the reply letter doctrine. Self-authenticating documents (FRE 902) do not require extrinsic evidence of authenticity.
Judicial Notice
Judicial notice under Federal Rule of Evidence 201 allows a court to accept a fact as established without requiring formal proof because the fact is either generally known within the trial court's jurisdiction or can be accurately and readily determined from reliable sources. In civil cases, judicially noticed facts are conclusive. In criminal cases, the jury is instructed that it may, but is not required to, accept the noticed fact. Judicial notice promotes efficiency by eliminating the need to prove indisputable facts.
Burden of Proof
The burden of proof encompasses two distinct concepts: the burden of production (bringing forth sufficient evidence to make a prima facie case) and the burden of persuasion (convincing the trier of fact to the required standard). In civil cases, the standard is preponderance of the evidence (more likely than not). In criminal cases, the prosecution bears the burden of proving guilt beyond a reasonable doubt. Some civil matters — such as fraud and termination of parental rights — require clear and convincing evidence, an intermediate standard.