Expert Witnesses

Question 1

When are opinions of non experts (lay opinion) allowed?

Answer 1

Testimony in the form of an opinion is limited to one that is:
• Rationally based on the witness’s perception,
• Helpful to clearly understanding the witness’s testimony or to determining a fact in issue, and
• Not based on scientific, technical, or other specialized knowledge within the scope of Rule 702.

Question 2

What is an expert witness and when may they testify?

Answer 2

A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if:
• the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue;
• the testimony is based on sufficient facts or data;
• the testimony is the product of reliable principles and methods; and
• the expert has reliably applied the principles and methods to the facts of the case.

Question 3

What two types of reliability are required of expert testimony?

Answer 3

1) Reliable principles underlying the expert’s approach, and

2) Reliable application of those principles to the facts of the case.

Question 4

What must an expert have to be qualified as an expert witness?

Answer 4

witness must establish his qualification by pointing to numerous factors such as knowledge, skill, experience, training, or education.
• Degree is not necessary to qualify as an expert. E.g., car technician

Judge qualifies a witness to testify as an expert.

Question 5

How can expert witnesses use inadmissible evidence?

Answer 5

Evidence that is otherwise inadmissible may be admitted, but the jury can only use it to evaluate the reliability of the expert, and not the truth of the matter.

Question 6

When may an expert offer and opinion on an ultimate issue and when may they not?

Answer 6

• An opinion is not objectionable just because it embraces an ultimate issue.
  
  • Exception - in a criminal case, an expert witness must not state an opinion about whether the defendant did or did not have a mental state or condition that constitutes an element of the crime charged or of a defense. Those matters are for the trier of fact alone.