Blood Stain Pattern Analysis Lecture

foreign there we go hi I&#39;m Matthew Steiner Matt is a certified senior crime scene analyst he&#39;s explained crime scene forensics in technique critique so that&#39;s a really interesting yet very illegal way to get DNA from somebody today I&#39;m going to show you how to analyze various blood stain patterns so we&#39;ll learn the techniques forensics experts used to investigate blood stain patterns ranging from easy to difficult so normally when we go to a crime scene it&#39;s not set up like this unless we have some sort of Dexter X crime scene where the Killer really planned it out today we&#39;re doing on set for safety purposes for us at crime scenes when we investigate them safety is number one we want to protect ourselves I think we various bloodborne pathogens that we&#39;re dealing with and secondly we don&#39;t want to contaminate the crime scene so we don&#39;t want the hairs and fibers on ourselves the DNA that&#39;s shedding off Us Falling onto our evidence at a crime scene we&#39;d wear multiple layers of gloves if we&#39;re going to be handling evidence and then we&#39;d want to wear eye protection if there&#39;s like a splash Hazard with blood that hasn&#39;t been dried so our Tyvek suit covers most of our body including our feet because we want to be introducing our shoe wear Impressions into a crime scene or destroying evidence that&#39;s there so normally I&#39;d be wearing a mask but I don&#39;t think it&#39;s a really good look for talking on camera next we&#39;re going to talk about the three main categories of blood stains that we can encounter at a crime scene foreign we&#39;re going to be using defibrinated sheep&#39;s blood we have taken the fibrin out of this blood fibrin is a protein that&#39;s in our plasma that causes our blood to clot so if we use regular whole blood that had fibrin in it we&#39;d have a clotted mess inside this bottle let&#39;s say pattern analysts correlate the appearance of these blood stain patterns at a crime scene to a mechanism by which they were created it isn&#39;t a crystal ball it isn&#39;t like the way TV presents it where a prime scene investigator walks into a scene and could tell you every single action that happened inside that crime scene from beginning to end analysts can correlate the static blood stains at a crime scene with Dynamic forces that create them so we look at is specific stain patterns and we could figure out how they possibly were created and then with that we could show a small window of time not the whole crime but that this type of force could have created this sort of pattern so passive patterns are patterns that are created without any sort of outside external Force other than gravity or contact so we&#39;re going to first start off with avoid dropping blood at 90 degrees to see what we get so I&#39;m going to take pipette and a small amount of blood and hold it directly above and drop it so when our sphere of blood strikes the surface at 90 degrees we have a very even round circle at a crime scene but also what affects the way our blood stain looks is the surface itself we have Plexiglas and we notice that the edge characteristics of our bloodstain are very even now that we observed the way that blood acts on a smooth surface let&#39;s try tile which has a little bit of texture to it one drop of blood straight down onto a different surface now you can see a little bit of scalloping around the edges there that&#39;s because of the surface texture so the scalping is just the different ways that we describe the edge characteristics of blood stains so it could be smooth uniform it could be scalloped or it could be spiny so now we change the surface to a rougher surface wood so we can see a vast difference from where we started where we have smooth edge characteristics now we have the spinier pattern because that blood drop is being disrupted by the surface itself and we can also see we have some satellite stains satellite stains are stains that come off of parent stain so this main stain here is my parent stain in this case because the disruption they are being forced out from the center of it we also see satellite spatter when blood is being dripped into blood typically at a crime scene especially with stabbings we want to look for these drip patterns it could be that the suspect accidentally cuts themselves and they&#39;re moving around a crime scene and fleeing the crime scene and they could leave blood trails that we could follow next we&#39;re going to be looking at contact transfer stands a transfer pattern is a passive pattern where we have a bloody surface coming in contact with another surface and then sometimes we could actually figure out what made that transfer whether it was a hand or a weapon or someone&#39;s clothing I mean that&#39;s the best type of evidence that we could have at a crime scene is we have the victim&#39;s blood and we have the suspect&#39;s impression there&#39;s very few explanations of how that happens so we&#39;re going to start off with a shoe our impression and blood so this could be our victim Walking Through Blood creating patterns in our crime scene or this could be the suspect&#39;s shoe wear impression we&#39;re going to coat the bottom of the shoe and we&#39;re going to transfer the pattern at the bottom of the shoe to our clean surface so I have my shoe wear that&#39;s completely coated in Blood and then inside that crime scene we have a transfer of that pattern and we&#39;ll notice is that that pattern gets lighter and lighter as we move along what we don&#39;t see with our naked eye we could find later on with chemicals like luminol or blue star so we could see a continuation of that pattern as someone walks away from a crime scene sometimes we see transfer patterns in textiles so next we&#39;re going to take some blood saturate a portion of our genes with it and we&#39;re going to transfer that onto our surface so sometimes in real crime scenes these get misinterpreted as the lines of minutia in your fingerprints or palm print we would see is that unlike fingerprints or just straight lines either way we would document this and collect it and send to the lab and then under magnification analyze it so next we&#39;re going to discuss how movement could affect these transfer stain patterns so I&#39;m going to take some blood and put it onto my hand and then move that across the surface so if I touch the surface and then move my hand we see what&#39;s called Feathering the effect of movement on blood just like if I took a paintbrush and moved it across the wall in the beginning it would be darker but eventually it would get lighter so if this Feathering effect helps us interpret movement at a crime scene this could be found at a crime scene in many different ways one could be our suspect has blood on their hands and they move it across a clean surface and another very common way that we see these patterns at a crime scene are what&#39;s called drag marks we have a victim that&#39;s bleeding and either they&#39;re moving through the scene or someone&#39;s dragging them through the scene and we&#39;d see the same effect that Feathering going towards the body next we&#39;re going to cover a flow patterns and that is the volume of blood being affected by gravity so we can see here is that gravity is pulling upon that blood and pulling it down on our surface at crime scenes this may be very valuable evidence when we observe our victims injuries person had an injury to their shoulder if they&#39;re standing or if their body is erect that flow pattern should go straight down in our arm but if they&#39;ve been moved or this movement or that injury was caused when they&#39;re laying down we&#39;d see a different flow pattern so next we&#39;re going to discuss saturation and pooling pattern that we have at a crime scene saturation pulling patterns could tell us that someone is bleeding in a certain part in a crime scene for a period of time you know sometimes when we see Bubbles at a scene that could mean that we have a expirated pattern or a pattern that&#39;s coming from an airway but let&#39;s pop those because we don&#39;t want but what this could tell me is that we had accumulation of blood there and that there has been no movement because if this happened and then we moved the shirt we would see that the blood would move in that direction typically we&#39;ll see this on mattresses or beds or bedding and then it would absorb a little more so now we&#39;re going to have an accumulation of blood on a non-porous surface and we&#39;ll see pooling so pooling and saturation it&#39;s the same mechanism we&#39;re looking at just the accumulation of blood but pulling the blood is not being absorbed into the surface for pools of blood what we&#39;ll see with actual whole blood that has fibrin in it they will dry a lot slower than it would in something that absorbent but also we&#39;re going to see over a period of time is clotting inside that pool and then sometimes we&#39;ll see affect what&#39;s called serum separation so the edges of this will be clear where we see the plasma of the blood as it separates so now we&#39;re moving on to the spatter category of bloodstain pattern analysis with this category of blood stains we&#39;re looking at some sort of external force on an open source of blood so I&#39;m going to do is I&#39;m going to put a small amount of blood on our wood here I&#39;m going to strike it with a hammer and what we should see is that impacts batter on the Plexiglas in front of us put on my goggles I&#39;m going to put my hood up give us a small amount of blood here all right ready there we go so as you can see not only do we have impact spatter on the plexiglass in front of us we also have it on our suspect here okay so we applied Forest to an open source of blood and we have a resulting impact stain our stain pattern what we&#39;ll notice is directly opposite where the force was applied we have our blood striking that surface at 90 degrees so these stains that we have right here near the bottom are circular but the further we move away from that Source these blood stains are now hitting this surface at an angle so our stains are more elliptical bludgeoning would be the most common way that we get these stains but it could be that we have the force of a bullet passing through somebody so we have a phenomenon called forward spatter and back spatter so if someone is shot and if bullet passes through say their shoulder we have blood going in the direction of the force or with the bullet out of the exit but we also have blood going the opposition of the force and that&#39;s what we call back spatter first up we started by creating different patterns so we could analyze Next Step we&#39;re going to look at something a little more difficult [Music] next we do is calculate the area of convergence that&#39;s a two-dimensional area on our surface if we draw a line through the long axis of several stains where all these lines will meet they should converge in an area somewhere in the center here what I want to do is pick several stains that are elliptical from different sides of the pattern we&#39;re looking at this to solve where this blood came from I&#39;m going to start with this stain here and I&#39;m going to line up so that I&#39;m drawing a line through the long axis of my stain so this is where the tail is going to help me out to figure out the directionality but also to line up my ruler and then sometimes what we&#39;ll do is just kind of show for a jury an arrow the direction that stainless going so then I&#39;ll move around the pattern from different sides of it and draw through different stains so this isn&#39;t done in every crime scene but when we have a pattern like this we have elliptical stains along the outside and we have some circular stance towards the inside this is the perfect opportunity for us to do some analysis I could keep going and draw more lines through more stains and it should all be coming back to the same general direction so if this was on the wall and this is very low you know this could be very powerful evidence to show that you know that that was low to the ground where this impact happened since we identify different stains that are striking our surface at different angles we&#39;re going to figure out the angle of impact that these stands hit our surface we do that by measuring the length of the stain we divide it into the width of the stain and the arc side of that number will give us our angle of impact so we&#39;re measuring stains we always want to use millimeters allows us for smaller measurements so what we could also use is a digital caliper and that will give us precise sub millimeter measurements so I want to measure the length of the stain the long axis of the stain so this is 3.1 millimeters and then I&#39;d measure the width of it so I&#39;m measuring the widest part of the stand that&#39;s 1.7 millimeters we&#39;re going to divide 3.1 into 1.7 so if we do the arc sine of that number that will give us the angle of impact which is 33.25 if you had a regular ruler you would just have to round up to the closest millimeter so in this case this stain is four millimeters and then we measure the width of it it is two millimeters so we would divide four into two which gives us 0.5 and the arc sine of 0.5 is 30 degrees and we can see this basically at the same distance from our Center but just on the other side if we look at this two dimensionally we know that these lines of our area of convergence meet here but if I want to think about it three-dimensionally that my blood is coming from somewhere above it here so the next step will be is that we&#39;re going to calculate the area of origin if it&#39;s coming in at a right angle here I have a triangle so this would be my adjacent side of the triangle I know that it&#39;s 90 degrees from here so that&#39;s my right triangle and then this side that the path takes is the hypotenuse of the triangle and so if I know the distance from my stain to my area of convergence and I want to figure out how far away my area of origin is here in space if I do the tangent of that I could figure out the side like sohcahtoa when we analyze blood sense in a field I always feel it&#39;s better to do all these methods we should be coming up with similar results but if you messed up somewhere you know one of those is going to be correct next up we&#39;re going to try something a little more difficult interpreting relationships foreign there&#39;s an adage that forensic science is the art of observation governed by science so we have observed our stain patterns at our crime scene and we&#39;re going to interpret how these possibly were created so if I go to a crime scene and I see that there&#39;s some clothing there eventually I&#39;m going to recover this but after I recover it and I see that there&#39;s passive stance underneath it I know that this came after this that this wasn&#39;t in place that this was placed afterwards and if I don&#39;t see a transfer of blood on here it could be that this was a ready dry by the time this clothing went on top of it so now we&#39;re looking at a passive drug pattern this could be the victim&#39;s blood this could be the suspect&#39;s blood we won&#39;t know until we sample it and send it off for analysis what we can interpret from this could be movement so if this trail of blood is leading away from the scene we would see those Tails going in a direction of travel now we&#39;re looking at a white pattern we have a pre-existing stain that something came in contact and moved through it so we could see from our discussion earlier Feathering that the directionality is coming towards me something is passively dripping blood that could be a weapon that could be a victim that could be our suspect and then something later on comes through it that could be someone trying to clean up the stain this could also be that maybe someone was dragged through this or there was some sort of movement through that stain so that was a white pattern now we have a swipe pattern blood is on something here and we could see again that same Feathering going in the direction of travel we have a transfer pattern with movement which is a swipe pattern there&#39;s blood on something and then we&#39;re just moving that in a direction usually when it&#39;s a white pattern we could see those original stains so the drawing and then someone tries to wipe them off with a cloth now we&#39;re looking at a cast off pattern so this is a subcategory spatter that&#39;s a projection mechanism so blood is on an object and removing that object in space that could be someone&#39;s hand that could be a pipe that could be a bat that could be a knife and as that object moves blood will be flung off it and we have these very distinct linear patterns or curvy linear patterns at a crime scene if we see these cast off patterns they can go up the walls they can go across the floor and even onto the ceiling so we&#39;re looking at a spatter pattern but we have a normally continuous drops of blood that are being interrupted or blocked by something and that gives us a pattern What&#39;s called the void sometimes we have crime scenes where there&#39;s something important that would be in that pool or in that pattern or that spatter pattern and it&#39;s been removed so it could be someone&#39;s bag or a cell phone their wallet if I had a crime scene where someone was bludgeoned and adjacent to his head was the complete absence of uh blood spatter looking to the left of him there was a spatter pattern it didn&#39;t line up what we determined was that the curtains inside of the hotel room were open at the time of the crime and then closed later on we&#39;ve gone over how these patterns are created or different categories of patterns and what we can interpret from these patterns at a crime scene this is not a simple process this stuff takes time training and experience and beyond that there&#39;s no absolutes with any of this there&#39;s no one specific answer then it&#39;s only that one answer I hope you guys learned a lot [Applause]

foreign there we go hi I&amp;#39;m Matthew Steiner Matt is a certified senior crime scene analyst he&amp;#39;s explained crime scene forensics in technique critique so that&amp;#39;s a really interesting yet very illegal way to get DNA from somebody today I&amp;#39;m going to show you how to analyze various blood stain patterns so we&amp;#39;ll learn the techniques forensics experts used to investigate blood stain patterns ranging from easy to difficult so normally when we go to a crime scene it&amp;#39;s not set up like this unless we have some sort of Dexter X crime scene where the Killer really planned it out today we&amp;#39;re doing on set for safety purposes for us at crime scenes when we investigate them safety is number one we want to protect ourselves I think we various bloodborne pathogens that we&amp;#39;re dealing with and secondly we don&amp;#39;t want to contaminate the crime scene so we don&amp;#39;t want the hairs and fibers on ourselves the DNA that&amp;#39;s shedding off Us Falling onto our evidence at a crime scene we&amp;#39;d wear multiple layers of gloves if we&amp;#39;re going to be handling evidence and then we&amp;#39;d want to wear eye protection if there&amp;#39;s like a splash Hazard with blood that hasn&amp;#39;t been dried so our Tyvek suit covers most of our body including our feet because we want to be introducing our shoe wear Impressions into a crime scene or destroying evidence that&amp;#39;s there so normally I&amp;#39;d be wearing a mask but I don&amp;#39;t think it&amp;#39;s a really good look for talking on camera next we&amp;#39;re going to talk about the three main categories of blood stains that we can encounter at a crime scene foreign we&amp;#39;re going to be using defibrinated sheep&amp;#39;s blood we have taken the fibrin out of this blood fibrin is a protein that&amp;#39;s in our plasma that causes our blood to clot so if we use regular whole blood that had fibrin in it we&amp;#39;d have a clotted mess inside this bottle let&amp;#39;s say pattern analysts correlate the appearance of these blood stain patterns at a crime scene to a mechanism by which they were created it isn&amp;#39;t a crystal ball it isn&amp;#39;t like the way TV presents it where a prime scene investigator walks into a scene and could tell you every single action that happened inside that crime scene from beginning to end analysts can correlate the static blood stains at a crime scene with Dynamic forces that create them so we look at is specific stain patterns and we could figure out how they possibly were created and then with that we could show a small window of time not the whole crime but that this type of force could have created this sort of pattern so passive patterns are patterns that are created without any sort of outside external Force other than gravity or contact so we&amp;#39;re going to first start off with avoid dropping blood at 90 degrees to see what we get so I&amp;#39;m going to take pipette and a small amount of blood and hold it directly above and drop it so when our sphere of blood strikes the surface at 90 degrees we have a very even round circle at a crime scene but also what affects the way our blood stain looks is the surface itself we have Plexiglas and we notice that the edge characteristics of our bloodstain are very even now that we observed the way that blood acts on a smooth surface let&amp;#39;s try tile which has a little bit of texture to it one drop of blood straight down onto a different surface now you can see a little bit of scalloping around the edges there that&amp;#39;s because of the surface texture so the scalping is just the different ways that we describe the edge characteristics of blood stains so it could be smooth uniform it could be scalloped or it could be spiny so now we change the surface to a rougher surface wood so we can see a vast difference from where we started where we have smooth edge characteristics now we have the spinier pattern because that blood drop is being disrupted by the surface itself and we can also see we have some satellite stains satellite stains are stains that come off of parent stain so this main stain here is my parent stain in this case because the disruption they are being forced out from the center of it we also see satellite spatter when blood is being dripped into blood typically at a crime scene especially with stabbings we want to look for these drip patterns it could be that the suspect accidentally cuts themselves and they&amp;#39;re moving around a crime scene and fleeing the crime scene and they could leave blood trails that we could follow next we&amp;#39;re going to be looking at contact transfer stands a transfer pattern is a passive pattern where we have a bloody surface coming in contact with another surface and then sometimes we could actually figure out what made that transfer whether it was a hand or a weapon or someone&amp;#39;s clothing I mean that&amp;#39;s the best type of evidence that we could have at a crime scene is we have the victim&amp;#39;s blood and we have the suspect&amp;#39;s impression there&amp;#39;s very few explanations of how that happens so we&amp;#39;re going to start off with a shoe our impression and blood so this could be our victim Walking Through Blood creating patterns in our crime scene or this could be the suspect&amp;#39;s shoe wear impression we&amp;#39;re going to coat the bottom of the shoe and we&amp;#39;re going to transfer the pattern at the bottom of the shoe to our clean surface so I have my shoe wear that&amp;#39;s completely coated in Blood and then inside that crime scene we have a transfer of that pattern and we&amp;#39;ll notice is that that pattern gets lighter and lighter as we move along what we don&amp;#39;t see with our naked eye we could find later on with chemicals like luminol or blue star so we could see a continuation of that pattern as someone walks away from a crime scene sometimes we see transfer patterns in textiles so next we&amp;#39;re going to take some blood saturate a portion of our genes with it and we&amp;#39;re going to transfer that onto our surface so sometimes in real crime scenes these get misinterpreted as the lines of minutia in your fingerprints or palm print we would see is that unlike fingerprints or just straight lines either way we would document this and collect it and send to the lab and then under magnification analyze it so next we&amp;#39;re going to discuss how movement could affect these transfer stain patterns so I&amp;#39;m going to take some blood and put it onto my hand and then move that across the surface so if I touch the surface and then move my hand we see what&amp;#39;s called Feathering the effect of movement on blood just like if I took a paintbrush and moved it across the wall in the beginning it would be darker but eventually it would get lighter so if this Feathering effect helps us interpret movement at a crime scene this could be found at a crime scene in many different ways one could be our suspect has blood on their hands and they move it across a clean surface and another very common way that we see these patterns at a crime scene are what&amp;#39;s called drag marks we have a victim that&amp;#39;s bleeding and either they&amp;#39;re moving through the scene or someone&amp;#39;s dragging them through the scene and we&amp;#39;d see the same effect that Feathering going towards the body next we&amp;#39;re going to cover a flow patterns and that is the volume of blood being affected by gravity so we can see here is that gravity is pulling upon that blood and pulling it down on our surface at crime scenes this may be very valuable evidence when we observe our victims injuries person had an injury to their shoulder if they&amp;#39;re standing or if their body is erect that flow pattern should go straight down in our arm but if they&amp;#39;ve been moved or this movement or that injury was caused when they&amp;#39;re laying down we&amp;#39;d see a different flow pattern so next we&amp;#39;re going to discuss saturation and pooling pattern that we have at a crime scene saturation pulling patterns could tell us that someone is bleeding in a certain part in a crime scene for a period of time you know sometimes when we see Bubbles at a scene that could mean that we have a expirated pattern or a pattern that&amp;#39;s coming from an airway but let&amp;#39;s pop those because we don&amp;#39;t want but what this could tell me is that we had accumulation of blood there and that there has been no movement because if this happened and then we moved the shirt we would see that the blood would move in that direction typically we&amp;#39;ll see this on mattresses or beds or bedding and then it would absorb a little more so now we&amp;#39;re going to have an accumulation of blood on a non-porous surface and we&amp;#39;ll see pooling so pooling and saturation it&amp;#39;s the same mechanism we&amp;#39;re looking at just the accumulation of blood but pulling the blood is not being absorbed into the surface for pools of blood what we&amp;#39;ll see with actual whole blood that has fibrin in it they will dry a lot slower than it would in something that absorbent but also we&amp;#39;re going to see over a period of time is clotting inside that pool and then sometimes we&amp;#39;ll see affect what&amp;#39;s called serum separation so the edges of this will be clear where we see the plasma of the blood as it separates so now we&amp;#39;re moving on to the spatter category of bloodstain pattern analysis with this category of blood stains we&amp;#39;re looking at some sort of external force on an open source of blood so I&amp;#39;m going to do is I&amp;#39;m going to put a small amount of blood on our wood here I&amp;#39;m going to strike it with a hammer and what we should see is that impacts batter on the Plexiglas in front of us put on my goggles I&amp;#39;m going to put my hood up give us a small amount of blood here all right ready there we go so as you can see not only do we have impact spatter on the plexiglass in front of us we also have it on our suspect here okay so we applied Forest to an open source of blood and we have a resulting impact stain our stain pattern what we&amp;#39;ll notice is directly opposite where the force was applied we have our blood striking that surface at 90 degrees so these stains that we have right here near the bottom are circular but the further we move away from that Source these blood stains are now hitting this surface at an angle so our stains are more elliptical bludgeoning would be the most common way that we get these stains but it could be that we have the force of a bullet passing through somebody so we have a phenomenon called forward spatter and back spatter so if someone is shot and if bullet passes through say their shoulder we have blood going in the direction of the force or with the bullet out of the exit but we also have blood going the opposition of the force and that&amp;#39;s what we call back spatter first up we started by creating different patterns so we could analyze Next Step we&amp;#39;re going to look at something a little more difficult [Music] next we do is calculate the area of convergence that&amp;#39;s a two-dimensional area on our surface if we draw a line through the long axis of several stains where all these lines will meet they should converge in an area somewhere in the center here what I want to do is pick several stains that are elliptical from different sides of the pattern we&amp;#39;re looking at this to solve where this blood came from I&amp;#39;m going to start with this stain here and I&amp;#39;m going to line up so that I&amp;#39;m drawing a line through the long axis of my stain so this is where the tail is going to help me out to figure out the directionality but also to line up my ruler and then sometimes what we&amp;#39;ll do is just kind of show for a jury an arrow the direction that stainless going so then I&amp;#39;ll move around the pattern from different sides of it and draw through different stains so this isn&amp;#39;t done in every crime scene but when we have a pattern like this we have elliptical stains along the outside and we have some circular stance towards the inside this is the perfect opportunity for us to do some analysis I could keep going and draw more lines through more stains and it should all be coming back to the same general direction so if this was on the wall and this is very low you know this could be very powerful evidence to show that you know that that was low to the ground where this impact happened since we identify different stains that are striking our surface at different angles we&amp;#39;re going to figure out the angle of impact that these stands hit our surface we do that by measuring the length of the stain we divide it into the width of the stain and the arc side of that number will give us our angle of impact so we&amp;#39;re measuring stains we always want to use millimeters allows us for smaller measurements so what we could also use is a digital caliper and that will give us precise sub millimeter measurements so I want to measure the length of the stain the long axis of the stain so this is 3.1 millimeters and then I&amp;#39;d measure the width of it so I&amp;#39;m measuring the widest part of the stand that&amp;#39;s 1.7 millimeters we&amp;#39;re going to divide 3.1 into 1.7 so if we do the arc sine of that number that will give us the angle of impact which is 33.25 if you had a regular ruler you would just have to round up to the closest millimeter so in this case this stain is four millimeters and then we measure the width of it it is two millimeters so we would divide four into two which gives us 0.5 and the arc sine of 0.5 is 30 degrees and we can see this basically at the same distance from our Center but just on the other side if we look at this two dimensionally we know that these lines of our area of convergence meet here but if I want to think about it three-dimensionally that my blood is coming from somewhere above it here so the next step will be is that we&amp;#39;re going to calculate the area of origin if it&amp;#39;s coming in at a right angle here I have a triangle so this would be my adjacent side of the triangle I know that it&amp;#39;s 90 degrees from here so that&amp;#39;s my right triangle and then this side that the path takes is the hypotenuse of the triangle and so if I know the distance from my stain to my area of convergence and I want to figure out how far away my area of origin is here in space if I do the tangent of that I could figure out the side like sohcahtoa when we analyze blood sense in a field I always feel it&amp;#39;s better to do all these methods we should be coming up with similar results but if you messed up somewhere you know one of those is going to be correct next up we&amp;#39;re going to try something a little more difficult interpreting relationships foreign there&amp;#39;s an adage that forensic science is the art of observation governed by science so we have observed our stain patterns at our crime scene and we&amp;#39;re going to interpret how these possibly were created so if I go to a crime scene and I see that there&amp;#39;s some clothing there eventually I&amp;#39;m going to recover this but after I recover it and I see that there&amp;#39;s passive stance underneath it I know that this came after this that this wasn&amp;#39;t in place that this was placed afterwards and if I don&amp;#39;t see a transfer of blood on here it could be that this was a ready dry by the time this clothing went on top of it so now we&amp;#39;re looking at a passive drug pattern this could be the victim&amp;#39;s blood this could be the suspect&amp;#39;s blood we won&amp;#39;t know until we sample it and send it off for analysis what we can interpret from this could be movement so if this trail of blood is leading away from the scene we would see those Tails going in a direction of travel now we&amp;#39;re looking at a white pattern we have a pre-existing stain that something came in contact and moved through it so we could see from our discussion earlier Feathering that the directionality is coming towards me something is passively dripping blood that could be a weapon that could be a victim that could be our suspect and then something later on comes through it that could be someone trying to clean up the stain this could also be that maybe someone was dragged through this or there was some sort of movement through that stain so that was a white pattern now we have a swipe pattern blood is on something here and we could see again that same Feathering going in the direction of travel we have a transfer pattern with movement which is a swipe pattern there&amp;#39;s blood on something and then we&amp;#39;re just moving that in a direction usually when it&amp;#39;s a white pattern we could see those original stains so the drawing and then someone tries to wipe them off with a cloth now we&amp;#39;re looking at a cast off pattern so this is a subcategory spatter that&amp;#39;s a projection mechanism so blood is on an object and removing that object in space that could be someone&amp;#39;s hand that could be a pipe that could be a bat that could be a knife and as that object moves blood will be flung off it and we have these very distinct linear patterns or curvy linear patterns at a crime scene if we see these cast off patterns they can go up the walls they can go across the floor and even onto the ceiling so we&amp;#39;re looking at a spatter pattern but we have a normally continuous drops of blood that are being interrupted or blocked by something and that gives us a pattern What&amp;#39;s called the void sometimes we have crime scenes where there&amp;#39;s something important that would be in that pool or in that pattern or that spatter pattern and it&amp;#39;s been removed so it could be someone&amp;#39;s bag or a cell phone their wallet if I had a crime scene where someone was bludgeoned and adjacent to his head was the complete absence of uh blood spatter looking to the left of him there was a spatter pattern it didn&amp;#39;t line up what we determined was that the curtains inside of the hotel room were open at the time of the crime and then closed later on we&amp;#39;ve gone over how these patterns are created or different categories of patterns and what we can interpret from these patterns at a crime scene this is not a simple process this stuff takes time training and experience and beyond that there&amp;#39;s no absolutes with any of this there&amp;#39;s no one specific answer then it&amp;#39;s only that one answer I hope you guys learned a lot [Applause]

Transcript for:Blood Stain Pattern Analysis Lecture

Transcript for:
Blood Stain Pattern Analysis Lecture