If you like crime shows, stories about mysteries and really interesting forensic science, this story is for you.
It is forensic science week across the country. Gov. Mark Dayton also has declared it forensic science week in Minnesota to highlight the work of the state’s top crime detectives — not the guys and gals you see on television, but real-life scientists solving complicated mysteries that affect the lives and deaths of real people.
We know that DNA evidence has changed criminal investigations, led to arrests and convictions — and helped exonerate those wrongly convicted of crimes.
The same is true for another type of forensic science. I recently had the rare opportunity to meet with the forensic scientists who work as crime scene investigators for the Minnesota Bureau of Criminal Apprehension to learn about some groundbreaking research they’ve been working on in the area of blood stain pattern analysis.
Yes, blood stains and blood spatter.
The forensic scientists at the BCA have done one of the most extensive studies ever of this kind of blood evidence, which is almost always found at crime scenes where a victim has died as a result of violence. The scientists have conducted countless experiments using super high speed video to observe and analyze blood stains and how blood behaves under various circumstances.
Their work involves “examining the size, shape and distribution of blood stains at a crime scene or on different pieces of evidence and trying to determine what mechanisms may have occurred that got the blood to that location,” said Steven Swenson, a BCA forensic scientist.
Swenson is an expert in the analysis of blood stains and spatter patterns. While his work is likely not a topic you’d discuss over dinner, for the forensic scientists at the BCA and the law enforcement agencies, being able to understand the compelling story blood tells at a crime scene helps them provide answers for loved ones.
It also could help convict people who commit violent crimes — or bring freedom or exoneration to the accused.
“We are really trying to understand the story and figure out how we can best solve the puzzle,” Swenson said.
Scientists conducted the videotaped experiments using real human blood donated to the BCA for the research. The videos were filmed at a speed of 10,000 frames per second, providing extremely detailed images of what blood does when it hits a surface or something hits it. Here’s what they contain:
Video No. 1 — BCA forensic scientist Terry Laber slowed down the video and showed us a muzzleloader firing. The image you see is of a big plume of smoky gas that comes from the gun barrel. Laber told us that it was once believed blood from a victim, along with the gases, would be sucked back into the barrel. His experiment proved that is not the case at all. Those gases will push blood away, rather than sucking it into the barrel of the gun.
“It explains why we do not see blood on the weapon or the shooter in a lot of the shooting cases that we do,” Laber said. “This helps us understand the formation of the blood stain pattern.”
Video No. 2 — Laber also showed us what happens when blood drops into a pool of blood. Often at a crime scene, there will be a pool of blood and someone dripping more blood into the pool of blood. The scientists wanted to see whose blood would spatter out of this pool. Will it be the pool or the person who is bleeding? To visualize that, they took coffee creamer, which is about as thick as blood, and dropped it into a pool of blood. This ultimately helps investigators determine what samples to focus on at a crime scene.
So what spattered? Take a look for yourself.
Video No. 3 — Laber also placed blood on the wrench handle and let it drip onto a piece of paper. The blood, because of its elasticity, forms a long column and if you watch closely, the column will snap and then flip little drops of blood to either side.
“People were observing next to main drops of blood, little drops, but they never knew exactly how they were formed and this shows exactly how they were formed,” Laber said.
Where the blood lands and how it lands can show direction, distance, type of weapon and may ultimately determine the killer. Blood patterns created in the lab are patterns these scientists often see at crime scenes.
Every year the BCA investigates 10 to 15 cases where blood patterns or spatter have become key evidence. Swenson recently testified in a Blue Earth County murder case where the suspect used a hammer as a weapon. He also analyzed evidence in a trial earlier this year where a jury found a man guilty of stabbing an Oakdale nanny.
Swenson said he is always affected by the humanity of what he sees at crime scenes. He hopes his work in the area of blood stain evidence helps more families find the answers they’re looking for about what happened to their murdered loved ones.
“That part is interesting. It shows how fragile life is and that’s definitely something that we see a lot of,” he said. “You don’t take for granted those small things in life.”
You can watch the forensic scientists in action at 10 p.m. Thursday on KARE 11 News.