In today’s post, I am looking at Locard’s Exchange Principle, named after the famous French Criminologist, Edmond Locard. Succinctly put, the exchange principle can be stated as “every contact leaves a trace.” This is perhaps well explained by Paul L. Kirk in his 1953 book, Crime Investigation: Physical Evidence and the Police Laboratory:
Wherever he steps, whatever he touches, whatever he leaves, even unconsciously, will serve as a silent witness against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects. All of these and more bear mute witness against him. This is evidence that does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are. It is factual evidence. Physical evidence cannot be wrong, it cannot perjure itself, it cannot be wholly absent. Only human failure to find it, study and understand it can diminish its value.
In other words, the perpetrator involved in a crime brings something into the scene and at the same time takes something with them. They both can be used against the perpetrator as forensic evidence. As a huge fan of mystery stories and shows, I was very interested when I first heard about this principle. Rather than the applications in the forensics science, I was thinking about it from a cybernetics standpoint. When two people converse with each other, their interactions can be viewed in the light of Locard’s exchange principle. Both of them bring something into the conversation, and in turn take something with them. There is a cross-transfer of ideas with successful conversations. To quote the late German philosopher, Hans-Georg Gadamer:
The true reality of human communication is such that a conversation doesn’t simply enforce one opinion over and against the other, nor does it simply add one opinion to another, as a kind of addition. Rather, true conversation transforms both viewpoints.
It may be challenged that true conversations do not always take place. However, this is something that we can strive for. At the same time, we need to be mindful not to treat information as a commodity that can be passed around. Just because we convey a message by speaking it out aloud, it does not mean that the message is conveyed. As the great cybernetician, Heinz von Foerster, would say – the hearer not the utterer determines the meaning of a message.
Claude Shannon, the father of Information Theory, looked in depth on successful transmission of messages. He noted:
The fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point. Frequently the messages have meaning; that is, they refer to or are correlated according to some system with certain physical or conceptual entities. These semantic aspects of communication are irrelevant to the engineering problem. The significant aspect is that they are selected from a set of possible messages.
Shannon’s model had a source (a sender of a message), a transmission medium (a channel with noise and distortion) and a receiver. The sender had to encode the message and sent it through the medium. The receiver had to receive the message and decode the message and reconstruct the message. The receiver had to have a set of possible messages so that they were able to properly decode the message such that any distortion or noise introduced in the medium can be compensated for. Shannon came up with a quantitative measure for the amount of information in a message – entropy. This is also a measure of surprise. For a message with low entropy, there is little surprise. For a message with high entropy, there is a lot of surprise, and this requires redundancy to ensure that the message is properly conveyed. For example, if the sender is sending a message, “011”, then the sender can repeat the message three times. “011 011 011”. Thus, if the message gets distorted such as “011 001 011”, the receiver is able to still decode the message as “011”. Curiously, if the message has a full amount of surprise, then the receiver will not be able to decode the message. Thus, if the message was entirely new information, the message will not be decoded successfully, no matter how much redundancy is entered. This is the whole point of cryptic messages.
We are autopoietic entities, which means that we are informationally closed. No information can come into our organization from the outside. We are closed to information coming in. Any information is generated from within when we are exposed to perturbations from the outside. I have previously talked about this before. See here and here. We generate the information based on the perceptual network evolved specifically for us. We cannot pass information around as a commodity. Autopoeisis is the brainchild of Humberto Maturana and Francesco Varela. They noted:
Autopoietic systems do not have inputs or outputs. They can be perturbated by independent events and undergo internal structural changes which compensate these perturbations.
When we are communicating as part of being at the gemba, we have to keep in mind that we may not completely understand the meaning as the way the utterer intended. In a similar way, the hearer, the other person, may not have understood the meaning as we had intended the meaning to be. Even though we both may have heard each other 100%, we may not have communicated 100% (the way we think at least). Instead, I am interpreting what the other person is saying, and trying to respond to what I think the other person has said. The same applies to the other person. We are both interpreting each other. We are both trying to perturb each other with the hope that the meaning that is being generated has some similarity to what we want to communicate. It is here that I appreciate Locard’s Exchange Principle. We are coming in and leaving something (not the entire thing) at the scene, and at the same time, we are taking something (again not the entire thing) with us as we leave the scene. When we communicate, we are hopefully inspiring each other. Communication is never achieved 100%, but some transfer of ideas takes place resulting in transformation of existing ideas. As Gadmer indicated, when we communicate, the ideas do not get added on top of each other in an additive fashion. Rather, the ideas get transformed. When we are at the gemba, we should be keen on listening with intent. We should be open to receiving the ideas from others and be willing to transform. We should be mindful that what we are saying will not be understood the way we want it to be. We should also be mindful of our non-verbal communication. Most of the time, we can tell a lot by how a leader acts. A leader often talks the talk that we want to hear. However, their actions often talk the loudest.
I will stop with the great George Bernard Shaw’s wonderful quote on communication:
The biggest problem with communication is the illusion that it has occurred.
Please maintain social distance and wear masks. Stay safe and Always keep on learning…
In case you missed it, my last post was The Truth About True Models: