“The DNA profile from the crime scene shares the same alleles as the DNA from the accused.”  That is a statement of fact or an expert opinion, but whatever it is it is not lay opinion.

“I ride bicycles a lot.  When the brake pads start to wear down, it’s riskier to ride in the rain.”  Now, what is that?  Expert or lay opinion?

And why do we care?  Because to proffer expert opinion evidence notice and discovery requirements must be met and the judge’s gatekeeping role has particular significance.  Yet deciding the question is not easy.  Consider the bicyclist – the person has experience but no real specialized knowledge; but on the other hands the community of non-bicyclists might not know this.

This inquiry was provoked by students in a mock trial competition where a police officer was investigating an accident that severely injured a parachutist.  The officer was also a parachutist who had jumped numerous times.  The officer examined the parachute worn by the injured jumper, found that certain parts were mishandled and/or missing, and concluded that

the main parachute was probably prepared for the jump the wrong way, because there were cords wrapped around one side of the chute, which would have prevented it from inflating properly.  The reserve chute also had a problem. In order for the reserve to work, you need these particular pieces to work, the SLinks, which allow the cables to activate and move from the pulling cord to the emergency cords on each side of the skydiver body, over the shoulders. The Slinks were missing. Only a suicidal skydiver would jump without the Slinks properly installed!

The answer is not clear.  While the final sentence about “only a suicidal skydiver” is blatant opinion evidence, and probably not “helpful,” is the rest purely factual; and if not, is it lay or expert?  Consider the words “probably prepared for the jump the wrong way, because there were cords wrapped around one side of the chute, which would have prevented it from inflating properly.”  Fact mixed with opinion for sure, but lay or expert?

A review of caselaw only begins to give an answer but at least provides the tools for good advocacy on both sides of the argument.  Let’s start with the general principles:

The text of the Federal Rules…it specifies that lay opinion testimony is not based on “specialized knowledge within the scope of Rule 702.” Fed. R. Evid. 701(emphasis added)…[T]he question is not whether the opinion requires specialized knowledge, as all opinion testimony does, but whether the specialized knowledge is sufficiently specialized to fall within the scope of [702].

The Advisory Committee Notes to Rule 701 prove instructive on this point, distinguishing between specialized knowledge within the scope of Rule 702 and personal knowledge: “courts have permitted lay witnesses to testify that a substance appeared to be a narcotic, so long as a foundation of familiarity with the substance is established.” Fed. R. Evid. 701 advisory committee’s note to 2000 amendment. This is because “[s]uch testimony is not based on specialized knowledge within the scope of Rule 702, but rather is based upon a layperson’s personal knowledge.”…Similarly, Professor Imwinkelried (who is cited several times by the United States Supreme Court in Daubert) explains that in drawing the line between lay and expert testimony,

the judiciary should bear in mind that the real basis for distinguishing between lay and expert opinion testimony is whether the opinion rests in part on vicarious experience. In the past, when police officers have testified about the modus operandi for certain crimes, the courts have almost automatically leaped to the conclusion that the officer was testifying in an expert capacity. However, the classification should turn on the experiential basis of the opinion rather than the witness’ occupation. If a patrol officer proffered the opinion based solely on his or her personal observation of that type of crime, the opinion should be categorized as lay.

Edward J. Imwinkelried, The Taxonomy of Testimony Post-Kumho: Refocusing  on the Bottomlines of Reliability and Necessity, 30 Cumb. L. Rev. 185, 212 (2000)(emphasis added).

L.L. v. State, 189 So. 3d 252, 257-258, 2016 Fla. App. LEXIS 5262, *11-14, 41 Fla. L. Weekly D 854, 2016 WL 1357736.

But not all courts follow this demarcation.  Here is what the Utah Supreme Court wrote:

specialized knowledge is knowledge “with which lay persons are not familiar.” Other courts have similarly defined specialized knowledge as “beyond the ken of the average juror” or outside the knowledge of a “civilian bystander.”…The mere percipience of a witness to the facts on which he wishes to tender an opinion does not trump rule 702. Otherwise, a layperson witnessing the removal of a bullet from a heart during an autopsy could opine as to the cause of the decedent’s death….

…[T]he test for determining whether testimony must be provided by an expert is whether the testimony requires that the witness have scientific, technical, or other specialized knowledge; in other words, whether an average bystander would be able to provide the same testimony.

In this case, Chief Adair’s testimony that methamphetamine is usually sold in quarter-to-half-gram portions is not the type of testimony that could be offered by an average bystander who had observed Rothlisberger’s and Althoff’s arrests.

State v. Rothlisberger, 2006 UT 49, P31-P34, 147 P.3d 1176, 1185, 2006 Utah LEXIS 144, *28-32, 560 Utah Adv. Rep. 4.  Put simply, the Chief knew more than the average citizen.

And what about Kansas?  When a motorcycle owner testified to the amount of damage caused by an accident, he did so based on his ‘specialized experience:’

he had owned five or six motorcycles during his “whole life” and had a “basis of knowledge . . . to provide” an estimate. He was, he said, “real knowledgeable when it comes to motorcycles and repairs”; he had several friends who owned motorcycle shops and rode sport bikes like the damaged motorcycle as well as Harleys.

State v. Sasser, 305 Kan. 1231, 1241-1247, 391 P.3d 698, 706-709, 2017 Kan. LEXIS 119, *18-30, 2017 WL 1194858

In Kansas, the version of Rule 701 in effect at the time of the trial did not make clear that if the opinion derived from specialized knowledge it did not constitute lay testimony.  But the Kansas Supreme Court asserted that even under the amended rule this would be acceptable lay testimony:

In this case, most of Zuber’s testimony was limited to facts—the history of his motorcycle ownership and familiarity with their repairs through personal experience or his associations with friends and his brother and their related employment. Two of his statements can be classified as his (probably unsurprisingly flattering) opinions of the depth and breadth of his motorcycle knowledge. Those statements are not challenged. Sasser takes issue only with the district judge’s ruling to allow Zuber to recite the $1,000 to $1,500 value he gave police for the likely value of the damaged motorcycle’s repairs. The judge regarded it as lay opinion testimony, a characterization we do not question today.

Zuber’s testimony was not based on information that was so scientific, technical, or specialized that it cried out for greater court control, even if we were to analyze this case under the revised statute. The district judge’s ruling was not arbitrary, fanciful, or unreasonable; and it was not based on an error of law or of fact.

Id.  In other words, not so specialized.

The Utah and Kansas cases are irreconcilable. So how about the Advisory Committee Notes to F.R.E. 701?  Here is where they draw the line:

most courts have permitted the owner or officer of a business to testify to the value or projected profits of the business, without the necessity of qualifying the witness as an accountant, appraiser, or similar expert…Such opinion testimony is admitted not because of experience, training or specialized knowledge within the realm of an expert, but because of the particularized knowledge that the witness has by virtue of his or her position in the business. The amendment does not purport to change this analysis. Similarly, courts have permitted lay witnesses to testify that a substance appeared to be a narcotic, so long as a foundation of familiarity with the substance is established.  Such testimony is not based on specialized knowledge within the scope of Rule 702, but rather is based upon a layperson’ s personal knowledge. If, however, that witness were to describe how a narcotic was manufactured, or to describe the intricate workings of a narcotic distribution network, then the witness would have to qualify as an expert under Rule 702.

USCS Fed Rules Evid R 701.  Again, helpful but not decisive.

How about academic analysis?  Professor Anne Poulin proposes the following:

If a witness has a broad base of relevant experience, but brings no methodology to bear in drawing inferences, the witness’s opinion should be treated as lay opinion. A witness who is merely applying everyday reasoning to draw inferences from the combination of the witness’s experience and the relevant observed facts should not be granted the latitude accorded an expert. Taking this approach, courts would not allow a witness to give expert opinion based solely on experience without determining that the witness had a reliable and specialized mode of analysis, and had applied it to a reliable basis. Most experience-based opinion would be evaluated as lay opinion and restricted accordingly.

In addition, the rule governing lay opinion, Rule 701, should be given more bite. The courts should scrutinize lay opinion to make sure that the witness’s knowledge supports the inferences reflected in the opinion.


In an email, Professor Ed Imwinkelreid suggested the following:

 In the case of a layperson, he or she must:

–have personal knowledge of the case-specific fact; and

–must derive their generalization solely or primarily through personal knowledge.

In the case of an expert, he or she may:

–gain their knowledge of the case-specific fact through any of the methods recognized by FRE 703; and

–rely on out-of-court sources for their generalization, e.g., lectures they had in school, treatises they have read, etc.–the notion of vicarious experience…


Professors Poulin and Imwinkelreid get it – the determination is more about the reasoning process applied and the source(s) of knowledge and less about the labeling.  But finding the line may be elusive in some cases, and jurisdiction-dependent. And for the parachute witness, those words “probably prepared for the jump the wrong way, because there were cords wrapped around one side of the chute, which would have prevented it from inflating properly[]” are closer to “particularized” rather than “specialized” knowledge and apply what Poulin calls “everyday reasoning,” so it may be safe to call it “lay.”