A Guide to Opinion and Expert Testimony Objections

An Overview of Opinion and Expert Testimony

Article VII (FRE 700 Series), otherwise known as the Opinion and Expert Testimony rules, provides guidance for the admissibility of a witnesses opinion and conclusions during their testimony.

A simple explanation and a reason why these rules exist is so that the court can tell the difference between bias and opinion from facts. Therefore, these rules lay out what is acceptable as testimony from lay (everyday people) and expert witnesses.

This article will go over the 5 rules that are laid out as:

  • Rule 701. Opinion Testimony by Lay Witnesses
  • Rule 702. Testimony by Expert Witnesses
  • Rule 703. Bases of an Expert’s Opinion Testimony
  • Rule 704. Opinion on Ultimate Issue
  • Rule 705. Disclosing the Facts or Data Underlying an Expert Opinion

Lay vs Expert. What’s the difference?

A witness can fall into two categories: lay or expert. Therefore, it’s good to know the differences between them.

  • A lay witness is your everyday person who is testifying the facts of what occurred, and not what they believe as an expert. For example, a lay witness can simply be the one who witnessed the crime of a bank robbery or the one who witnessed the victim falling inside a convenience store.
  • An expert witness is one that is qualified by a particular trait such as knowledge, skill, experience, training, or education and one that relies on scientific, technical, or specialized knowledge. They are allowed to infer what they believe using this knowledge and associated evidence when they are testified during trial. For example, a civil engineer can be entered in as an expert witness and can use research or domain knowledge to infer that a stop light was unsafe at a particular intersection.

Rule 701: Opinion Testimony by Lay Witness

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These rules allow certain opinions made by a lay witness to be heard. It explicitly defines what a lay witness is allowed to admit during testimony. However, in order for the testimony to be admitted, it must pass all three rules. The rules are:

  1. The witness must perceive these opinions out of their own senses (i.e., They came up with the conclusion using their senses)
  2. The witnesses opinion must advance the case or provide clarity to the case
  3. The witnesses opinion CANNOT include scientific or specialized knowledge.

If it passes all three rules, the opinion is allowed under Rule 701.

Rule 702: Testimony by Expert Witnesses

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These rules allow opinion testimony by a witness who is qualified to answer under their expert knowledge, skill, experience, training, or education. If they are not an expert in the specified field, they are not allowed to make opinion testimony under the subject.

In order for opinion testimony for an expert witness can be entered, it must pass the following tests:

  1. The witness must be an expert in their admitted field (i.e., A witness must be an expert in their field(s) before they can answer the question)
  2. The testimony must advance the case or provide clarity

These tests only apply to Mock Trial. In the real world, it must pass a few additional tests concerning the validity of the facts and data.

Rule 703: Bases of an Expert’s Opinion Testimony

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In Mock Trial, Rule 703 is a continuation of Rule 702. Specifically, Rule 702 answers “can the person give an opinion?”. Rule 703 answers “can the person tell you why they can give an opinion?”

These rules allow opinion testimony by an admitted expert witness. The rule states that the expert witness must form their opinion from facts or data within the scope of their knowledge. To further define:

An expert witness may form an opinion from facts or data from these sources:

  1. Personal Observation (field of work)
  2. Information at Trial
  3. Other Sources (academic papers not cited by the expert, interviews)

For example, an expert witness that is entered as an expert in mechanical engineering can form opinions based on their personal experience as a mechanical engineer, information that was presented during trial, and third-party academic papers or interviews.

Rule 704: Opinion on Ultimate Issue

This rule is often misunderstood and confused. There are different rules for different types of cases. We will break it down into what to do for a civil case and a criminal case.

Ultimate Issue – The question(s) the jury has to answer based on what they’ve heard or seen in trial.

In both civil and criminal cases, an attorney cannot object when a witness is asked to testify about the ultimate issue.

What to do in a Civil Case when it comes to Ultimate Issue

  • Nothing. An opinion about the Ultimate Issue is not objectionable.

What to do in a Criminal Case when it comes to Ultimate Issue

  • An expert witness cannot make an opinions about the motive regarding the ultimate issue
  • For example, the expert witness cannot say “In my expert opinion, the defendant had the motive/mindset/intent to commit the crime.” This is objectionable.

Rule 705: Disclosing the Facts or Data Underlying an Expert Opinion

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This rule basically states that an expert may state an opinion without having to disclose the facts or data.

However, if  the expert witness does make an opinion and they are asked to disclose the facts or data, they have to disclose it. This will typically occur during cross examination where the opposing counsel may ask to clarify their opinions using facts and data.

Character Evidence: An In-Depth Guide

An Overview of Character Evidence

Character Evidence is when testimony or evidence is used against someone to prove their character personal traits.

For example, let’s say there was a case about a bank robbery and Character Evidence is used to say Mike robbed a convenience store in 2014. Since Mike robbed a convenience store in 2014, he could have robbed the bank. Does this make Mike guilty of robbing the bank? No

The reason why we have such rules is so that we do not prejudice the jury and piece together two facts. Just because Mike robbed a convenience store in 2014 does not make him guilty of robbing the bank.

The Character Evidence rules sit on two Articles of the Federal Rules of Evidence. The first being ARTICLE IV: RELEVANCE AND ITS LIMITS and ARTICLE VI: WITNESSES. The 400 level rules deal with Character Evidence and 600 level rules deal with Character Truthfulness. This article will go in-depth into these Character Evidence rules.

Rule 404 & Rule 405

These two rules deal with Character Evidence and the exceptions to them.

Rule 404

Character Evidence and its exceptions are described under Rule 404. It also offers exceptions.

Full Text: Rule 404. Character Evidence; Crimes or Other Acts

The Rules

Rule 404(a) – Evidence of a person’s character or character traits cannot be used as evidence. This type of evidence includes opinion and testimony of a person’s reputation.

Rule 404(b) – Evidence of a specific instance in time to prove a person’s character or character trait cannot be used as evidence. This type of evidence includes previous crimes or wrongdoings.

The Exceptions

Rules 404(a)(2) – These exceptions allow character evidence to be used in a criminal trial. However, these exceptions are only allowed in a criminal trial.

Rule 404(a)(2)(a) – This exception allows the prosecution to use character evidence to rebut the defendants use of character evidence if and only if the defense has used character evidence in their testimony.

Rule 404(a)(2)(b) – The use of this rule is limited by Rule 412 (Sexual Misconduct Cases). If the defendant offers character evidence of the victim and the evidence is admitted, the prosecution is allowed to: rebut that evidence and offer evidence that the defendant has a similar trait.

Rule 404(a)(2)(c) – This exception is only allowed in murder cases. This exception allows the prosecution to use Character Evidence to rebut the defendants evidence that the victim was the one who first aggressor or instigator.

Rule 404(b)(2) – These exceptions allow the use of previous crimes and wrongdoings to prove a person’s character. However, these exceptions can only be used in a criminal trial.

You can ONLY use this type of evidence to prove motive, opportunity, intent, preparation, plan, knowledge, identity, absence of mistake, or lack of accident.

You also must perform the following: prosecution must provide notice of evidence being offered at trial, before trial or during trial if the court excuses pretrial

Rule 405

Rule 405 goes over the methods of proving Character Evidence.

Full Text: Rule 405. Methods of Proving Character

  1. Reputation or Opinion – When character evidence is admissible, you can use this method of proving a person’s character or character traits using opinion or reputation testimony. For example, Josh is known for being an angry person.
  2. Instance of Conduct  – When character evidence is admissible, you can use this method of proving a person’s character or character traits by using evidence of prior conduct. For example, Mike robbed a convenience store before.

However, the only instance of where Instance of Conduct is allowed is when the character trait being proved is an essential element of the case. This goes back to the 404(b)(2) where it says you can only use instance of conduct evidence to prove motive, opportunity, intent, preparation, plan, knowledge, identity, absence of mistake, or lack of accident. 

Rule 608 & Rule 609

These rules deal character truthfulness for Character Evidence.

Rule 608

Full Text: Rule 608. A Witness

Rule 608 says that a witnesses credibility may be supported or attacked using character evidence if they truthful or untruthful. However, you cannot immediately support a witnesses credibility. You can only support a witnesses credibility after their character has been attacked for truthfulness.

Part B of this rule has an exception that says you cannot use evidence related to Specific Instances of Conduct to attack or support the truthfulness of a witness. Of course, there are two exceptions to this rule part of the rule under Rule 609. These exceptions are:

(1) these specific instances of conduct are only allowed when they are subjects of a criminal conviction

(2) these specific instances of conduct can be talked about during cross-examination. However, the only people allowed to talk about these specific instances are the: (a) the witness himself; or (b) another witness that was mentioned by the witness himself

Rule 609

Full Text: Rule 609. Impeachment by Evidence of a Criminal Conviction

If you want to use evidence of a criminal conviction to attack a witnesses character for truthfulness, the evidence must be:

✅admitted for felony convictions

✅must be admitted for a dishonest crime (crimen falsi)

However, this is where it gets even more complicated. If you want to admit past felony convictions, you must meet the following requirements:

✅ felony convictions are only admissible when the probative value outweighs the prejudicial effect (Rule 403)

✅ felony convictions are only admissible against witnesses that are not the defendant

✅ if the conviction is more than 10 years old, it is only admissible when the probative value substantially outweighs the prejudicial effect (reverse Rule 403)

Therefore, this rule is only effective if you can meet the three requirements for the first requirement and can meet the second requirement. This would need to take some substantial planning if you want to use such a piece of evidence.

The three other exceptions are described as:

Rule 609(c) – If the convict is issued a pardon, certificate of rehabilitation or an equivalent procedure, the conviction evidence is inadmissible.

Rule 609(d) – This only applies to juvenile adjudications. If you’re confused, a juvenile adjudication is similar to an adult conviction without the same level of consequences. This rule says that evidence for a juvenile adjudication is only admissible when its adult-equivalent of a conviction would be admissible under this rule.

Rule 609(e) – This exception makes it clear that if a conviction is under appeal, it does not make the conviction evidence inadmissible.

Relevance: A Basic Explanation

Overview of Relevance

There are six important rules that cover the basis of “Relevance.” However, this article will only cover Rules 401, 402, and 403. The other rules, Rules 404, 405, and 406, will be covered in another article going over Character Evidence.

Rule 401 and Rule 402

These Relevance rules are very basic. The basic premise for relevance is that any evidence admitted must be relevant. The rules, Rule 401 and Rule 402, define whether evidence is admissible or inadmissible. Rule 401 goes over the definition of relevance. Rule 402 says irrelevant evidence is inadmissible.

Key Takeaways

  • Relevance is a very Low Bar – The court favors evidence to be admitted. Therefore, not much is needed to establish the relevance of the evidence being entered.
  • Rules 401 and 402 Work Together – Rule 401 is followed by 402. Therefore, both rules work together. Rule 401 goes over the definition of relevance. Rule 402 says irrelevant evidence is inadmissible.
  • Relevance is Dangerous – Relevance is a dangerous objection. This is because the side that brings up the relevance objection must substantially prove that the evidence being admitted is irrelevant. It also dangerous because it allows your opponent to explain their case-in-chief to the jury.

Rule 403

Rule 403 is an extremely useful objection because it allows you to exclude evidence. The basic wording of the rule allows the court to decide to exclude evidence if they believe it would be prejudice or unfair to the case.

The exact wording says:

Rule 403. Excluding Relevant Evidence for Prejudice, Confusion, Waste of Time, or Other Reasons

The court may exclude relevant evidence if its probative value is substantially outweighed by a danger of one or more of the following: unfair prejudice, confusing the issues, misleading the jury, undue delay, wasting time, or needlessly presenting cumulative evidence.

However, there are a few catches to this objection.

  1. The evidence must be “substantially” or greatly unfair before it can be excluded.
  2. The rule is difficult to argue and win since the evidence must be “substantially” unfair.

The Balancing Equation (Prejudice vs. Probative)


The reason why this rule is difficult to use is that the court favors evidence being admitted than excluded. Therefore, it must protect against the misuse of this rule.

The court uses a BALANCING test to determine if the evidence is prejudice or probative. The difference between prejudicial and probative evidence is:

  • Prejudicial Evidence – Evidence that greatly prejudices (a preconceived opinion that is not based on reason) the jury
  • Probative Evidence – Evidence that can establish a fact

Key Takeaways

  • Rule 403 is a very High Bar – Unlike Rule 401 and Rule 402, with Rule 403, you must be able to establish that the evidence is not prejudice to the jury.
  • Evidence must be Substantially Prejudice – Evidence must prejudice the jury. The court will perform a balancing test to determine if it should be excluded from the trial