If the shoe fits: What forensic detectives can learn from footprints
What can investigators learn from footprints uncovered at crime scenes?
More than you might think, says Ed Adach, a detective who works in Toronto Police Service's forensics identification unit.
Adach specializes in footwear impression evidence, which involves identifying, collecting and examining footprints left at crime scenes that range from homicides to bank robberies. He says footprints, much like fingerprints, have distinct physical characteristics — cuts, nicks, different wear patterns — that are unique to each individual shoe.
Someone Knows Something sat down with Adach to discuss how forensic footwear analysis can play a pivotal role in crime scene investigations.
The transcript below has been edited for length and clarity. Watch the full video above.
ED ADACH: Any time I hear of a bad guy jumping over the bank counter or variety store counter, I just go, "Oh yeah. I'm coming to that scene because I know there's going to be a footprint there waiting for me."
Most impressions are invisible. It's a matter of how I can enhance that footprint to make it visible. And then I can collect it.
I can look at it and sometimes I can say, "Yeah, I recognize that. That's a Converse or a Nike Air Force One or whatever." I can tell myself. But if I don't recognize it —which is often because there's thousands of different styles — I can take the image, a photograph of the image, and I'll send it to the RCMP.
They can plot the types of patterns that are on the bottom of the shoe. Now what it does is it searches all the manufacturer's types of shoes that are within the database — thousands of different manufacturers, thousands and thousands of different styles.
What are accidental characteristics?
If the computer comes back with possibilities and they can look and go, "Oh yeah, it looks like this type of shoe." And they can send that back to me. Once the shoe is collected, I can compare it to the crime scene impression. The class characteristics are the manufacturer's pattern.
It's those accidental characteristics that make that shoe unique, that say yes, that shoe made that crime scene impression.- Ed Adach
So you may have thousands of the same type of shoe and they would leave the same impression, depending on their size.
But the other type of characteristics we're looking for are the accidental characteristics — these randomly acquired cuts and nicks occur on the bottom of the shoe as you're walking around. And it's those accidental characteristics that make that shoe unique, that say yes, that shoe made that crime scene impression.
Society has got those impressions of footwear impressions, of what we can do from Sherlock Holmes, in novels and that — their gait, how they walk. The depth of the foot in soil depends on the density of the soil much more than the weight of the person.
The most I can say with a footprint is if I've got the entire impression, I can estimate the height of the person but that's just an estimate. It's a good investigative tool. I'm not going to go to court and say he's guilty because he's 6 foot 2 inches and the footprint is a size 12 and a half.
What information can be gleaned from a footprint?
Beauty of forensic evidence and footwear impression evidence is it can help eliminate suspects. We want to find out that out in the beginning of the investigation. We don't want to drag somebody through an entire investigation if I can tell them right from the get-go — and I have many times — no, that's not your suspect. This is the shoe you're looking for.
There are other things that I can see at the crime scene. You can see from the impressions themselves who's gone where, who's doing what.
You have a homicide scene where a person is bludgeoned to death. In this case, there was sock impressions that had slight bit of blood on the bottom and he's walking throughout the house.
The footwear impressions are able to give you a visual of what actually occurred at the time.- Ed Adach
I spray the floor with a chemical that enhances the blood impressions. You can see where the person's gone to get the scissors and a hammer and pages from a Bible. You can see the movement within the apartment. The footwear impressions are able to give you a visual of what actually occurred at the time.
That evidence can be extremely damning. Especially when you have the cuts and nicks on the bottom of the shoe, I can say without a doubt that is the shoe that made it.
This transcript has been edited for length and clarity. Watch the full video at the top of this post.