About This Thing They Call Evidence
When we talk about conducting investigations and solving mysteries, what we’re actually talking about is gathering evidence. Evidence solves crime. Nothing more, nothing less. But, what exactly do we mean by the term evidence?
A Quick Definition
In its simplest form, evidence is just a set of reliable facts that tend to establish the truth or falsehood of a given narrative. As investigators, it’s important that we build our narrative from the evidence, and not the other way around. Our job always starts with gathering evidence first, and then (when possible) constructing a comprehensible narrative based on the evidence after that.
Some evidence is provided by objects, such as a latent fingerprint found on a murder weapon. Other evidence is provided by people, such as a person testifying to something they saw happen with their own eyes. Evidence is everywhere and — depending on what incident you’re investigating — could be nearly anything.
In our current world of information overload where an incomprehensible amount of new data is created every day, the key to investigations is learning how to efficiently cut through all this noise, gossip, and oceans of irrelevant info to arrive at those items that actually tell us something useful. In many ways, the goals of investigators and data analysts are one and the same: to find the facts that matter.
Two Broad Categories of Evidence
Evidence generally falls into one of two categories: direct or circumstantial.
If you cornered any seasoned investigator on the question of which type of evidence they would prefer to find during an investigation, direct evidence would win every single time. But in reality, cases don’t always play out that way. In a perfect world, direct evidence would be available for collection during every inquiry. But I’ll let you in on a little secret — the world’s not perfect. Sometimes the only evidence available to the investigator is circumstantial, and it can make for a compelling case when properly analyzed. As the saying goes, you have to play the cards you’re dealt.
Direct Evidence
Direct evidence is defined as “direct proof of a fact, such as testimony by a witness about what that witness personally saw or heard or did.” You don’t need any deductive reasoning to interpret this kind of data — it’s just plain as day.
If John saw Wanda hit her no-good husband Earl over the head with a hammer, then John would be able to testify to what he saw and offer direct evidence of Wanda’s guilt (though if I know anything about Earl, he probably had it coming — late 90’s country music humor, anyone?).
Circumstantial Evidence
Circumstantial evidence is a step removed from direct evidence and is defined as “proof of one or more facts from which one can find another fact.” Think of this as algebraic evidence. If faced with the equation a + 3 = 5, we can deduce the unknown value (a) from the known value (3).
Back to our earlier example, let’s say John is standing outside Wanda’s front door and hears a loud “thud” sound come from inside the house. He then sees Wanda walk out of the door holding a hammer. He proceeds to walk into the house and finds Earl lying on the floor with a big bloody bump on his head. At this point, John would possess circumstantial evidence that Wanda may have caused the injury to her husband (and probably shouldn’t be messed with either). While it’s not as good as direct evidence, it’s something that you sure don’t want to ignore.
What’s important to remember about circumstantial evidence is that a single piece of it generally proves nothing on its own. We can come up with a hundred different scenarios wherein the circumstantial evidence possessed by John doesn’t amount to Wanda’s guilt.
Imagine the same scenario with the added detail of a robber running from the back door of the house unseen by John at the same time Wanda is walking out of the front door holding the hammer. Was Wanda holding the hammer because she hit her husband over the head with it or because she was trying to protect herself from the robber who walloped Earl with a baseball bat? In this instance, John’s circumstantial evidence wouldn’t prove much of anything by itself.
The Key To Circumstantial Evidence
The key to circumstantial evidence is gathering multiple pieces of it from various sources and then seeing if they all point in a common direction. In this case, we may look at circumstantial evidence possessed by the next-door neighbor who saw the robber running from the back door holding a baseball bat, defensive wounds on Wanda caused by blunt force trauma, and the later recovery and analysis of the baseball bat that is found to contain Earl’s blood and subsequent DNA. When viewed holistically, this evidence would point to the fact that it was more likely the robber — and not Wanda — who caused the injury to Wanda’s husband.
We then might evaluate the circumstantial evidence obtained from these multiple sources against the direct evidence possessed by Wanda in which she says she saw the robber hit Earl in the head with a baseball bat. Taken together, all evidence gathered thus far in the investigation would be pointing in the same general direction — Wanda’s innocence and the robber’s guilt.
Of course, we could always uncover additional details that would cast doubt even on that conclusion. What if we were to pull Wanda’s phone records and find several calls between her and the robber in the days leading up to the attack on Earl? What if we uncovered a romantic relationship between Wanda and the robber? What would that indicate about Wanda’s possible involvement in the crime? Anything? Nothing at all?
Where Do We Stop?
And that’s what makes evaluating evidence so tricky. You don’t know how much is out there to start with, so it’s hard to ever know if you found it all. What if that one piece of evidence you never located was the thing that cast doubt on all your other conclusions? As investigators, how are we to deal with this problem of the unknown?
While there’s no easy answer, a qualitative research concept known as saturation can help us out here. Saturation is the point at which, with each new piece of evidence we find, it is becoming less and less likely that the evidence will point us in a new direction.
Let’s say we’ve gathered 100 different pieces of evidence in a single investigation. After the first 70, we might have put together a fairly clear picture of what happened. And then while gathering the last 30 pieces of evidence, we find that none of them point in any new direction from the first 70 pieces or indicate that there’s anything else for us to learn about what happened. At that point, it’s likely that we have reached saturation and could conclude our investigation without too much concern that we’re missing anything major.
Simply stated, you just have to keep digging until you’re finding the same thing over and over again. There’s really no magic number when you’re talking about a saturation level, but it’s probably going to take some time to get there. As much as investigation is an art and not a science, you just kind of know when you reach it.
So now that we have a general understanding of what evidence is and how it’s used during investigations, we’ll take a deeper dive with our upcoming posts into the three different types of evidence that are used to solve crimes: physical evidence, witness testimony, and suspect confession.
