If you’ve ever been on a jury
panel, you know that there are two types of witnesses: fact witnesses and
expert witnesses. There are different requirements for each role, and they serve
different purposes, though the ultimate purpose, of course, is to get to the
truth of the matter.
Fact witnesses are those individuals
who have personal knowledge about a particular matter. They have personally
experienced or observed something and are competent to testify about it
—truthfully. But they are not qualified or permitted to testify to
things beyond their personal knowledge. That will draw an objection of “speculation.”
Expert witnesses are not
expected to have personal knowledge of the matter at hand. Instead, they have a
particular expertise that is relevant to the case. They are permitted to
testify about standard procedures and what they would expect to see, now and in
the future, based upon their knowledge and experience of similar cases or
events. Before they can say a word about the case, however, there are specific
requirements to establish them as an expert and permit their testimony.
This includes things like education (degrees from reputable schools, or
specialized training, for example), experience (how familiar are they with
these types of cases, how many similar cases have they worked on/examined,
etc.), what the professional literature says, and whether that education and
experience makes them more knowledgeable about a matter than the average
When an expert testifies, he or she
must explain the basis of their opinion, the process by which they came to that
conclusion, and cite to any relevant studies, data, etc.
Both witnesses, the fact witness
and the expert witness, must testify only to things that are admissible under
the rules of evidence. For example, the fact witness cannot testify as to what other
people saw or heard, as that will likely draw a hearsay exception. They
cannot, generally speaking, make predictions about other situations, because
they don’t have the expertise to make those predictions based upon one
experience that they had.
Because I’m a lawyer, I tend to
view the social media posts around COVID19 in this same light.
If you have had the virus, you are
a “factual witness” who can “testify” to your experience. If someone near you
has had it, you can testify as to what you observed (e.g., “her
breathing was labored”), but probably not opine about that person’s experience
with the virus (e.g., “I’m sure it felt like breathing glass”). You also
are probably not qualified to predict how many people might get it, or what
their experiences are going to be.
Infectious disease specialists and
epidemiologists are the “expert witnesses” who cannot “testify” as to what your
experience was, but rather to the broader information and implications.
They are the ones that have the training and experience to do crunch the
numbers, to know what data is relevant and what isn’t, and to compare and
contrast a particular virus to other viruses.
If you share a post that poses as
an “expert witness,” but starts out, “My friend’s sister is a nurse and she
said…” I’m probably not going to read that (unless I know you and the friend,
and the nurse and trust what she has to say).
If your post starts out, “I created
my own spreadsheet and here is what is going to happen…” without telling me who
you are, why you are qualified to make those predictions, and the data upon
which you relied (with citations), I’m probably not going to pay any attention
If you cite CNN, FOX, MSNBC, or any
other news organizations, I am not going to rely on that, either, unless they
tell me who they received that information from, where the data came
from, and I can confirm that the statement is accurate and not taken out
If, on the other hand, I see a post
written by someone who has the expertise to speak on the matter, cites to their
(reliable) sources, and shows me the data, I will definitely listen. If they
tell me things like, “original predictions were X, but now that we have more
data from the U.S. (which is a different situation than China or Italy because
of Y), we have revised our predictions to Z” I will also pay attention, because
they are telling me not only what is different about their prediction,
but why it is different (again, with evidence to support their
Trials often have competing “experts,”
again, similar to the COVID-19 situation. Like jurors, we need to objectively
weigh the evidence presented by both sides to determine which is more
reliable, and which makes more sense. It is true that some jurors are “excused”
from serving due to real or potential biases. But because we are not “excusing”
anyone from participating in the conversation around COVID-19, we have to be
particularly careful about setting aside bias, and even what we think we
know based upon our own, limited experiences.
As Dan Heath says in his book, Upstream,
“Data takes you away from philosophical insights. You move away from
anecdotal fights about what people think is happening to what is happening.”
When you read a post about COVID-19,
especially one that seems particularly alarming, ask yourself:
- Who is the person making the statement? What “credentials”
do they have to suggest I should trust what they are telling me?
- Where did they get their data? Have they
provided citations so I can see the original source, and confirm that it
says what the author tells me it says?
- Does the statement appear to be objective and
factual, or is it full of adjectives designed to create an emotional response? In
other words, does it encourage me to think, or feel?
- Does the evidence support what they are telling
- Are there qualifiers that would change their “prediction,”
and do those qualifiers exist (e.g., when they start out “Absent any steps
taken to…” and I know there have been steps taken, how should I
interpret the data they have presented with the “Absent any steps taken”
Let’s be smart about this. Let’s
make sure we aren’t letting our fears drive our decisions. Let’s make sure that
the things we are reading are trustworthy. That doesn’t mean predictions and
recommendations won’t change; they likely will change, because this is a
new virus. But the trusted sources’ predictions and recommendations will change
with new and good data.
 Heath, D. (2020). Upstream:
the quest to solve problems before they happen. New York: Avid Reader
Press., citing a 2018 interview with Beth Sandor, head of Built for Zero, a
national effort to help communities end homelessness.