The Watch with Will Kennedy: Inside CMPD CSI Blood Pattern Analysis

CHARLOTTE, NC — It can seem like magic, but it’s actually science, with some math mixed in.

Crime scene investigators use blood pattern analysis to recreate some of the most violent crimes, helping put the criminals behind bars.

CMPD CSI takes us behind the scenes for an exclusive look at how it’s done.

The gory crime scene is a staple on TV and in movies, and it’s something that CMPD Crime Scene Search has to deal with as well.

“This is going to be kind of trial and error for us, since we’ve never done it,” says CMPD CSI Supervisor Roy Patterson. “We’ll see what happens.”

CMPD CSS took us to the range at the training academy, setting up demonstrations to recreate “real life” conditions.

“It’s supposed to be set up like you would find in a regular person’s head,” says Patterson during the setup. “So it’s supposed to give you the realistic blood spatter that you would normally have if you actually shot someone. ”

Dummy heads, filled with synthetic blood; shot, beaten, sliced and stabbed.

“You can see there’s clearly three slices, and we have two patterns up there,” says CMPD CSI Emily Carpernter after a demonstration.

Those patterns are often like a puzzle at a crime scene, with investigators trying to piece together what happened.

“So if we don’t know where they are, maybe they ran off and a trail ends,” says CMPD CSI Christine Cain. “Did they get in a car there? To helps us, because usually a blood trail is a good indicator of where they’re going, or where they came from.”

They may not know what type of weapon was used during a violent crime, or where victims and suspects were positioned. But they do have the tools to figure it out.

Blood Pattern Analysis can help tell the tale of the crime. And can support, or refute, witness testimony.

“If they’re getting beat where they’re on the ground, and they’re like ‘Oh no, they were standing and we were fighting!’,” says Cain. “But all the blood is indicating low on the ground, low on the wall. No, they’re probably laying down and you’re beating them.”

A suspect can claim self defense. The blood may say otherwise. Blood spatter is also influenced by the type of weapon used.

“The cast off isn’t as wide spread,” says Carpenter after smashing a dummy head with a machete. “So with my bat it was a little more spread out than with the machete, because it’s a sharper edge.”

Blunt force causes larger drops, and will be more directly concentrated nearby.

A gunshot wound creates smaller, tiny, droplets in a high-velocity spatter.

“He shot him right through here, through the head, like he was already on the ground,” says Carpenter.

Number and location of stains, plus volume of blood, influence how much useful information can be gathered.

“Different ways to document it,” says Cain. “So if it is everywhere, and there’s a lot of blood spatter on the walls, on the floor; we can separate them into areas, and kind of photograph and focus on one area at a time, to break it down so it’s not so overwhelming.”

BPA can be collected by cutting away stained surfaces or materials, photographing the stains, and drying and packaging stained items. Samples can be swabbed for DNA analysis, which can be critical in cases with victims, or if the suspect was injured.

“Swipe marks like this, where they’re dragging a body to a certain place, where hey, there’s marks going this way and then they stop all of a sudden,” explains Cain. “Did they drag them and roll them in a carpet, put them in a trunk, something like that?”

Pattern analysis and reconstruction uses direction and angle of spatter to establish areas of convergence and origin.

“We would photograph it,” says Carpenter. “We would put scales on this wall, across and down. And then you can actually measure the droplets.”

“An expert could string it, and you can actually get the height the person was standing who shot it,” say Cain.

Investigators use protractors, string and mathematical equations to determine if the victim was laying, sitting or standing; or how far away the suspect was.

The blood, or lack thereof, can make all the difference.

“We get one scene, and we have a pattern like this, and then nothing on the wall right here,” says Carpenter. “We know that something was sitting there.”

CMPD CSI says that blood pattern analysis has played a key role in several, recent high profile cases.