Relevancy and reasons for excluding relevant evidence - Qualifications of witnesses

Learning Outcomes

After reading this article, you will understand the rules governing the qualifications of witnesses in evidence law. You will be able to identify who is competent to testify, the requirements for personal knowledge and oath, and the special considerations for children, mentally impaired persons, and expert witnesses. You will be prepared to apply these principles to MBE-style questions.

MBE Syllabus

For MBE, you are required to understand the rules on who may testify as a witness and the reasons for excluding otherwise relevant evidence based on witness qualifications. This article covers:

  • The general rule of witness competency and its exceptions.
  • The requirements of personal knowledge and oath or affirmation.
  • Special rules for children, mentally impaired persons, judges, and jurors.
  • The qualification of expert witnesses and the court’s gatekeeping role.
  • The effect of state law on competency in diversity cases.

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

  1. Which of the following is NOT a general requirement for a person to be a competent witness?
    1. Personal knowledge of the matter
    2. Ability to communicate
    3. No prior criminal record
    4. Willingness to take an oath or affirmation
  2. In federal court, a 6-year-old child may testify if:
    1. The child is able to understand the duty to tell the truth and can communicate what was seen.
    2. The child’s parent consents to the testimony.
    3. The child has previously testified in court.
    4. The child is represented by counsel.
  3. Which statement about expert witnesses is correct?
    1. Only doctors and scientists can be experts.
    2. The court must find the expert is qualified and the testimony is reliable.
    3. Experts may testify only about facts, not opinions.
    4. Experts must have personal knowledge of the facts in every case.

Introduction

The Federal Rules of Evidence presume that every person is competent to be a witness unless a specific rule provides otherwise. However, not all relevant evidence will be admitted if the witness lacks the necessary qualifications. The rules on witness qualifications ensure that testimony is reliable and that the fact-finder receives evidence from individuals who can observe, recall, and communicate what is relevant to the case.

General Rule of Competency

All persons are presumed competent to testify. The court may exclude a witness only if the witness cannot meet the basic requirements of competency.

Key Term: Competency The legal capacity of a person to testify as a witness, generally presumed unless a rule provides otherwise.

Requirements for Witnesses

A witness must satisfy three main requirements:

  1. Personal Knowledge: The witness must have observed the matter and must testify from first-hand knowledge.
  2. Oath or Affirmation: The witness must declare that they will testify truthfully, either by oath or affirmation.
  3. Ability to Communicate: The witness must be able to communicate what they perceived.

Key Term: Personal Knowledge The requirement that a witness can testify only to matters they have directly observed or experienced.

Special Categories of Witnesses

Children

Children may testify if they have sufficient intelligence and can understand the obligation to tell the truth. There is no fixed minimum age for competency.

Mentally Impaired Persons

A person with mental impairment may testify if they can observe, recall, and communicate about the matter and understand the duty to tell the truth.

Judges and Jurors

Judges presiding over a case may not testify as witnesses in that case. Jurors may not testify as witnesses before the jury on which they serve, and may not testify about jury deliberations except in very limited circumstances.

Key Term: Dead Man's Statute A state law that may bar an interested party from testifying about communications with a deceased person in certain civil cases.

State Law in Diversity Cases

In federal diversity cases, state law governs witness competency if state law supplies the rule of decision for a claim or defense.

Expert Witnesses

An expert witness may testify if the court finds that:

  • The expert is qualified by knowledge, skill, experience, training, or education.
  • The expert’s testimony will help the trier of fact understand the evidence or determine a fact in issue.
  • The testimony is based on sufficient facts or data, is the product of reliable principles and methods, and the expert has reliably applied those principles and methods.

The court acts as a gatekeeper to ensure expert testimony is both relevant and reliable.

Key Term: Expert Witness A person qualified by specialized knowledge who may give opinion testimony to assist the fact-finder.

Worked Example 1.1

A 7-year-old child witnessed a car accident and is called to testify. The child can describe what happened and promises to tell the truth. The opposing party objects, arguing the child is too young.

Answer: The child may testify if the court finds the child can observe, recall, and communicate about the event and understands the duty to tell the truth. There is no fixed age bar.

Worked Example 1.2

In a federal diversity case, a party seeks to testify about a conversation with the now-deceased opposing party. The state where the court sits has a Dead Man’s Statute.

Answer: The federal court will apply the state’s Dead Man’s Statute to determine if the witness is competent to testify about the conversation.

Worked Example 1.3

A party offers an engineer as an expert witness on bridge safety. The court asks about the engineer’s qualifications and the methods used. The court then allows the testimony.

Answer: The court must find the engineer is qualified and that the testimony is based on reliable principles and methods. The judge acts as a gatekeeper for expert evidence.

Exam Warning

The MBE may test whether a witness’s lack of personal knowledge or inability to understand the duty to tell the truth makes them incompetent. Always check if the witness meets the basic requirements before considering the substance of their testimony.

Revision Tip

For MBE questions, remember: competency is presumed, but always check for personal knowledge, oath/affirmation, and ability to communicate. For experts, focus on qualifications and reliability.

Key Point Checklist

This article has covered the following key knowledge points:

  • All persons are presumed competent to testify unless a rule provides otherwise.
  • Witnesses must have personal knowledge, be able to communicate, and take an oath or affirmation.
  • Children and mentally impaired persons may testify if they meet these requirements.
  • Judges and jurors generally cannot testify in cases over which they preside or serve.
  • State law may govern competency in diversity cases.
  • Expert witnesses must be qualified and their testimony must be reliable and helpful.
  • The court acts as a gatekeeper for expert evidence.

Key Terms and Concepts

  • Competency
  • Personal Knowledge
  • Dead Man's Statute
  • Expert Witness
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