Hi, I'm Matthew steiner Matt is a certified senior crime scene analyst.

He's explained crime scene forensics in technique critique.

So, that's a really interesting yet very illegal way to get DNA from somebody today.

I'm gonna show you how to analyze various bloodstain patterns in this episode.

We'll learn the techniques forensics experts used to investigate bloodstain patterns ranging from easy to difficult.

Mhm.

So normally when we go to a crime scene, it'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're doing on set for safety purposes.

Mhm.

For us at crime scenes, when we investigate them, safety is number one, we want to protect ourselves.

I think the various blood borne pathogens that we're dealing with.

And secondly, we don't want to contaminate the crime scene so we don't want the hairs and fibers on ourselves.

The DNA that shedding off us falling onto our evidence at a crime scene.

We wear multiple layers of gloves.

If we're gonna be handling evidence and then we'd want to wear eye protection if there's like a splash hazard with blood that hasn't been dried.

So our tyveK suit covers most of our body, including our feet because we wanna be introducing our shoe wear impressions into a crime scene or destroying evidence that's there.

So, normally I'd be wearing a mask, but I don't think it's really good look for talking on camera.

Next we're gonna talk about the three main categories of bloodstains that we can encounter at a crime scene.

All right.

Mhm.

Today, we're gonna be using defib renate id sheep's blood.

We have taken the fiber and out of this blood fiber and is a protein that's in our plasma that causes our blood to clot.

So, if we use regular whole blood that had the fiber in it, we'd have a clotted mess inside this bottle bloodstain pattern, analysts correlate the appearance of these blood stain patterns at a crime scene to a mechanism by which they were created.

It isn't a crystal ball.

It isn't like the way tv presents it where a crime scene investigator walks into a scene and can tell you every single action that happened inside that crime scene from beginning to end, analyst can correlate the static bloodstains 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 forces other than gravity or contact.

So, we're going to first start off with dropping blood at 90° to see what we get.

So, I'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 a surface at 90 degrees, we have a very even round circle at a crime scene but also what affects the way our bloodstain looks is the surface itself.

We have plexiglass and we notice that the edge characteristics of our blood stains are very even now that we observe the way that blood acts on a smooth surface.

Let'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's because of the surface extra.

So the scalloping 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 would so we can see a vast difference from where we started where we have a smooth edge characteristics.

Now we have this spiny er 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 the stains that come off a parent stains.

So this main stain here's my parents 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're moving around the crime scene and fleeing the crime scene.

And they could leave blood trails that we could follow.

Next.

We're gonna 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 sometimes we can actually figure out what made that transfer, whether it was a hand or a weapon or someone's clothing.

I mean, that's the best type of innocent we could have at a crime scene.

So we have the victim's blood and we have the suspects impression.

There's very few explanations of how that happens.

So we're gonna start off with a shoe wear impressions in blood.

So this could be our victim walking through blood creating patterns in our crime scene, or this could be the suspect's shoe wear impressions were going to coat the bottom of the shoe and we're gonna transfer the pattern at the bottom of the shoe to our clean surface.

I have my shoe wear that's completely coated in blood and then inside that crime scene, we have a transfer of that pattern and we'll notice is that that pattern gets lighter and lighter as we move a lot.

What we don't see with our naked eye.

We could find later on with chemicals like Luminol and bluestar.

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're gonna take some blood saturated portion of our genes with it and we're gonna transfer that onto our surface.

So sometimes in real crime scenes these get misinterpreted as the lines of minutia in your fingerprints or a palm print we would see is that unlike fingerprints, are just straight lines.

Either way, we would document this and collected and sent to the lab and then under magnification, analyze it.

So next we're gonna discuss how movement could affect these transfer stain patterns.

So I'm going to take some blood and put it onto my hand and then move that across the surface.

So if I touched the surface and then move my hand, we see what'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 would be darker, but eventually it will get lighter.

So 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 a 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 or what's called drag marks.

We have a victim that is bleeding and either they're moving through the scene or someone's dragging them through the scene and we see the same effect that feathering going towards the body.

Next we're gonna cover flow patterns and that is the volume of blood being affected by gravity.

So we can see here is that gravity is pulling up on that blood and pulling it down on our surface at crime scenes.

This may be very valuable evidence when we observe our victim's injuries.

Person had an injury to their shoulder if they're standing or if their body is erect, that flow patterns should go straight down their arms.

But if they've been moved or this movement or that injury was caused when they're laying down, we'd see a different flow patterns.

So next we're going to discuss saturation and pooling patterns that we have at a crime scene saturation.

Pooling patterns could tell us that someone is bleeding in a certain part in the crime scene for a period of time.

You know, sometimes when we see bubbles at a scene, that could mean that we have a expiration pattern or a pattern that's coming from an airway.

But let's pop those because we don't.

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 will see this on mattresses or beds or bedding and then it would absorb a little more.

So now we're gonna have an accumulation of blood on a non porous surface and we'll see pooling.

So pooling and saturation, it's the same mechanism that we'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'll see with actual whole blood that has fiber and in it they will dry a lot slower than it would in something that's absorbent.

But also we're going to see over a period of time is clotting inside that pool and then sometimes we'll see affect what'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're moving on to the spatter category of bloodstain pattern analysis with this category of bloodstains were looking at some sort of external force on an open source of blood.

So I'm gonna do is I'm gonna put a small amount of blood on her.

Would here, I'm gonna strike it with a hammer.

And what we should see is that impact spatter on the plexiglass in front of us, put on my goggles, I'm gonna put my hood up, give us a small amount of blood here.

Alright, 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 for us to an open source of blood And we have a resulting impact stains are stained pattern.

What we'll notice is directly opposite where the force was applied.

We have our blood striking that surface at 90°. So these stains that we have right here near the bottom are circular.

But the further we move away from that source, these bloodstains are now hitting the 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 the 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's what we call back spatter.

First off, we started by creating different patterns that we could analyze.

Next step, we're gonna look at something a little more difficult.

Mhm.

Next we do is calculate the area of convergence.

That'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're looking at this to solve where this blood came from.

I'm going to start with this stain here and I'm going to line up so that I'm drawing aligned 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'll do is just kind of show for a jury and arrow the direction that steam was going.

So then I'll move around the pattern from different sides of it and draw through different stains.

So this isn't done at 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 can keep going and draw more lines to 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 identified different stains that are striking our surface at different angles, we're gonna figure out the angle of impact that these stains 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 sine of that number will give us our angle of impact.

So we're measuring stains.

We always want to use millimeters allows us for smaller measurements.

So what we could also uses a digital caliper and that will give us precise submillimeter measurements.

So I want to measure the length of the stain, the long axis of the stain.

So this is 3.1 mm And then I'd measure the width of it.

You're measuring the widest part of the stand, that's 1.7 mm.

We're gonna divide 3.1 into 1.7.

So if we do the arc sine of that number, that would 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.

And then we measure the width of it.

It is 2 mm so we would divide four into 2, which gives us .5 And the Arc sine of .5 is 30°. And if 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 coverage.

It's meat 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're going to calculate the area of origin.

If it's coming in at the right angle here, I have a triangle.

So this would be My adjacent side of the Triangle.

I know that it's 90° from here.

So that's my right triangle.

And then this side that the path takes us that have partners 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 so kato, when we analyze blood stains in the field, I always feel it's better to do all these methods where you 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're gonna try something a little more difficult interpreting relationships.

All right.