Opinions, Experts & Scientific Evidence

Question 1

What rule governs opinion tesimony by lay witnesses?

Answer 1

Rule 701

Question 2

Rule 701 lays out the limitations for a lay witness, what are they?

Answer 2

If a witness is not testifying as an expert, testimony in the form of an opinion is limited ot one that is:

(a) rationally based on the witness’s perception;
(b) helpful to clearly understanding the witness’s testimony or to determining a fact in issue; and
(c) not based on scientific, technical, or other specialized knowledge withint eh scope of Rule 702.

Question 3

What are the restrictions for an expert witness’s testimony in a criminal procedure under 704(b)?

Answer 3

In a criminal case, an expert wintess must not state an opinoin about whether the defendant did or did not have a mental state or condition that constitutes an element of the crime ro of a defense.

Those matters are for the trier of fact alone.

Question 4

Under rule 701, when does a witness’s opinon qualify as lay testimony?

Answer 4

If it is not based on scientific, technical, or other specialized knowlege.

Question 5

What rule govers expert testimony?

Answer 5

Rule 702

Question 6

What are 702’s prerequisit qualifications for being an expert?

Answer 6

Knowledge, skill, experience, training or education

Question 7

Under 702, when may a qualified witness testify as an expert?

Answer 7

A witness who is qualified as an expert by knowledge, skill, experience, training or education may testify in the form of an opinoin or otherwise if:

(a) the epxpert’s scientific technical or other specialized knowledge will help the trier of fact ot understand the evidence or to determine a fact in issue;
(b) the testimony is based on sufficient facts or data;
(c) the testimony is the product of reliable principles and methods; and
(d) the expert has reliably applied the principles and methods to the facts of the case.

Question 8

What rule governs the bases of an Expert?

Answer 8

Rule 703

Question 9

What may an expert rely upon as the basis of his opinion?

Answer 9

An expert may base an opinoin on facts or data in the case that the expert has been made aware of or personally observed.

This allows experts to rely on such evedence (sceintific studies, school records, textbooks read during training, statements made to the psychologist by friends & family during interviews) as a basis for their opionin, even if the evidence would otherwise be inadmissible under hearsay, so long as it is of a type reaonsbly relied upon by those in the field.

Question 10

May an expert witness base his opinion on facts the expert assumes but does not know to be true?

Answer 10

Yes, Williams v. Illinois (2012)

Question 11

What are the Daubert factors?

Answer 11

1. Testability;
2. Subjected to Peer Review/publication;
3. Known or potential rate of error;
4. Existence & maintenence of standards controlling the technique’s operation;
5. “General/widespread” acceptence

These factors aren’t rigid. Don’t need to check off each box. Can look at factors beyond these. Ultimately need to confirm the reliablity of the expert.

Question 12

What standard should appllate courts apply to a tiral court’s decision to admit or exlcude expert testimony?

Answer 12

Abuse of discretion

Question 13

Following Daubert what should a trial judge decide when faced with the prospect of an expert scientific testimony?

Answer 13

Faced with a proffer of expert scientific testimony, the trial judge must determine at the outset, pursuant to Rule 104(a), whether the expert is proposing to testify to (1) scientific knowlege that (2) will assist the triaer of fact to understand or determine a fact in issue.

Question 14

Does Daubert only apply to scientific knowlege?

Answer 14

No, General Electric Co v. Joiner says it applies to all expert opinions.