Forensic Science is History | Max Houck | TEDxUSFSP

so what happened here did you see the car drive on through the ice did you see it go through the ice did you see the person get out of the vehicle was it an accident was it a homicide and the bodies still in the car was it an attempted suicide we don't really know do we and that's the thing we weren't there to see it what we're left with are the remnants of the activity of interest and we have to piece those together to try to make sense out of what happened when I teach forensic science I teach it as a historical science like archaeology paleontology or geology and that's because we're all doing the same thing we're all taking what's left over from events we're interested in I'm trying to put them back together and make sense of them to reconstruct past events we're trying to make the absent present in a sense all of these Sciences center around sort of start from a novel written by Voltaire about a character named Tzadik and the book is called the book of fate Tzadik is a wanderer and he's walking through the woods one day and some of the Queen's retainers burst up and through the trees and see him and say have you seen the Queen's dog and he says small spaniel long years just had puppies limp and the left front paw yeah that's it have you seen it I don't even know what Queen had a dog then some of the King's staff burst through the trees looking for the King's prize stallion that's missing and Tzadik says excellent gallop er small hubs about five feet tall tale about three and a half feet long gold on the bridle silver shoes they're like exactly which way did it go I haven't seen any horses today so they immediately assume that he's lying and that he's a thief and they arrest him and they drag him in front of a judge as I dig explains his methodology which I will do to you and he's released and has other adventures in the book but this is important because this is the fur written example of what we could call a forensic philosophy and that's important because forensic science even though it's critical to our criminal justice system doesn't have an overarching philosophy it doesn't have a guiding set of principles and that's important Thomas Kuhn said that one of the things that differentiates science from pseudoscience is an internal corrective mechanism that is the ability to spot your errors correct them and make sure they don't happen again and that's what forensic science needs what we do is we construct reconstruct past criminal events right that's what we're using our abilities for now we don't get a perfect picture we don't get the name and address of the of the assailant what we get are as Freud notes slight and obscure traces and those are what we have to put together and the burden is on us to be able to interpret those accurately because lives are at stake George Cuvier was a pioneer of paleontology the study of fossils used proxy data to develop what he referred to as the principle of correlation of parts and what that means is if we find a fossil and it has large canines sharp teeth we can assume that it's a carnivore and that the rest of the body will follow suit Cuvier is principle is based on interrelated elements of a system so big teeth means a carnivore and the rest of the body will look like a carnivore in forensic science we do this routinely we see a fingerprint we assume there's a finger and behind the finger as a person that happens all the time but we don't think about it like that another example that we use in forensic science borrowed from geology that we don't know we borrowed from geology is called uniformitarianism and that's a big word that simply means that natural phenomena do not change in scope intensity or effect over time way to paraphrase that is that the present is the key to the past and what that means is if we look and see how volcanoes act today and the type of information that they produce today then what we're doing is seeing that process in action and we can apply that to the interpretation of volcanoes that erupted 200 years ago 200 million years ago it doesn't matter we can we can make these interpretations almost out without regard to time in forensic science we do the same thing we test fire bullets on the range today and we compare those two bullets from the crime scene two days two weeks two months two years ago again we can make these comparisons almost without regard to time now another principle that we borrow from geology without really knowing it is called the principle of superposition again a big word all that means is younger stuff is on top older stuff is on the bottom as you can see in this picture of sideling Hill from Maryland I used to drive past there all the time and always thought it was a great example you can see that the older layers of rock are below the younger layers which are on top this only makes sense if I spill coffee in a napkin the napkin was there first otherwise the coffee couldn't be spilled on it so the napkins slightly older than the coffee even if only by a second or so likewise at a crime scene when blood is shed the surface that lands on had to be there first otherwise the blood couldn't be shed on top of it now you might be thinking wow that's a really simple idea but crime scenes are complex environments and many crime scenes have been misinterpreted for a lack of knowledge about simple procedures like this another one that we borrow from geology is called the principle of lateral continuity and that means that materials in a layer are continuous until an object interrupts them so like cutting a cake for example now in forensic science we use the principle of lateral continuity in a couple of ways one for example let's say there's a broken pane of glass from a window and we can fit it back together like a that tells us if we can do that that that piece of glass was at one time a continuous piece of glass lateral continuity we can also do this with evidence that's transferred between an assailant and a victim during an assault so the the fibers that are transferred between the two individuals if they had no prior contact are taken as indications of lateral continuity during that assault and the more fibers we find and the more different kinds of fibers we find strengthen our interpretation of that lateral continuity finally we have absolute and relative chronology relative chronology is simply saying one thing is older or younger than another pretty straightforward absolute chronology is affixing a date or a time some quantitative value to an event so for example in forensic science if we find a receipt from a hardware store for a shovel on a bag of trash our box of trash bags and some duct tape and it's dated the day before we find the victim bagged taped and buried we call that a clue that in fact happened during one of my cases but using using those those measures in forensic science are important and you know we don't think of them that way I would be remiss talking only about borrowed principles without talking about one that comes from forensic science itself Edmond Locard who created the world's first forensic laboratory in Lyon France in 1914 developed this notion that now bears his name the Locard exchange principle states that when two objects come into contact information is exchanged pretty straightforward you're wearing boots you step in the mud you get mud on your boots you step on the floor you get mud on the floor you get yelled at you have tread on the boots that gets transferred to the mud as an impression again pretty straightforward but it's the central notion that powers forensic science the only problem is one principle isn't enough and I'll explain why there are almost 2200 people who have been wrongfully convicted and were exonerated those are just the ones we know about many of those people were wrongfully convicted based on erroneous notions of forensic science their lives inner liberties were taken from them what we need is that internal corrective mechanism we need a set of guiding principles a guiding philosophy to forensic science we as a discipline need to author our tomorrow so that we can prevent future wrongful convictions and allow innocent people to write to author their own tomorrow's thank you [Applause]

Channel: TEDx Talks

Views: 23,538

Keywords: TEDxTalks, English, Education, Crime, Criminal justice, Future, History

Id: kXAk_frXOxI

Length: 9min 54sec (594 seconds)

Published: Fri Jun 22 2018