Name: 犯罪現場の捜査官だけど「科学捜査について」質問ある？ | Tech Support | WIRED Japan
Uploaded: 2025-03-30T08:46:20.000Z
Duration: 16 min 23 s
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I'm here today to answer your questions from Twitter.

SNM 79 asks, ERP crime scene photo, dot, dot, dot.

Well, this was an old school method that they used to use to identify where a body was within a crime scene.

Later in an investigation, after bodies are removed, you could see where that body was and its position.

We no longer do this because of DNA contamination and trace evidence.

So instead of chalk now, we just take detailed photographs.

We'll document that scene with laser scanner.

That laser scanner is recording millions of points per second as it's spinning and also taking imaging as it's turning.

We could use virtual reality or augmented reality to go back and walk through that scene virtually now if we want to.

Forensic Field asks, question, what are the most popular methods for searching a crime scene?

The three most common ones are a line search, a grid search, and a zone search, though there are many others.

A line search, it would be a line of investigators, and it would search a crime scene in one direction.

We search in one direction and we don't find anything.

We can then turn that search at 90 degrees and search in another direction, and that's what's called a grid search.

Looking at it at an opposite angle at 90 degrees, sometimes you'll visualize that evidence.

The last most common search is a zone search, where you take a crime scene and you break it down into smaller parts.

As we discover evidence, we'll go around and we'll mark this evidence, and then we'll take additional photographs showing that scene with the numbers and then close-up views of the evidence.

So some markers will have a scale on it to show the size of it.

What you need to do is have a very systematic and methodical order that you pick to search these scenes.

Doing things at random, mailing about is not acceptable.

Joseph B. 977 asks, how many people got away at murder before forensic science improved and DNA?

I think another good question would be how many people were wrongfully convicted before forensic science?

Science is constantly improving, and our goal is the truth, and we just want our investigation to show that.

Years ago, a guy goes out to his car with a bag of trash next to his door, and he does what a lot of people would do, just kicks the bag.

Unbeknownst to him, there was a pipe bomb in that bag, and it detonated.

This was back in 2002, and we had no answers. 2006, I pull some of this evidence from storage, and I re-swabbed the wiring and the cap and the threading to the pipe bomb, and send that off for analysis, because in those short four years, DNA has advanced.

Inside of his car, he had more pipe bombs and automatic weapons.

So sometimes the work that we do not only can solve crimes, but it can also save lives.

Parker asks, how do forensics determine shit from blood spatter?

Are there experiments where you crack open dead bodies with different weapons under different circumstances?

First off, it's not blood splatter, it's blood spatter.

Blood from your arteries would be bright red, where the blood from your veins would be a darker color.

As that blood dries, it gets oxidized, it's contaminated by the crime scene, it can also change its color and tone.

If we have a suspect's name and we don't know what it is, oftentimes we'll do what's called a presumptive test, like we have here.

We'll tell you whether that sample could be blood.

You still have to sample it, you would send it to a laboratory, and they would say what it is and sometimes to whom it belongs to.

Cadavers, though, to your question, generally are not used for blood stain pattern analysis, but they are used at some universities.

And they put bodies in different circumstances.

So maybe they'll put the body in a car, they'll put it outside in the open in a field, different environments to see how those bodies decompose over time.

LRCF asks, how did one of the most infamous unsolved crimes committed on Valentine's Day in 1929 lead to new forensic science techniques and ballistics and a reform in gun control?

What they're referring to is the Valentine's Day massacre in Chicago in 1929.

Seven Irish mobsters were lined up against the wall and they were shot to death.

The weapons of choice in this crime was the Thompson submachine gun or Tommy gun.

Back then, anyone could walk into a store and purchase one of these weapons.

And because of the public outcry of this case, we got our first federal gun control law, which took these weapons out of the private sector's hand.

Also with this case was one of the first uses of forensic ballistic evidence.

Forensic ballistics is the study of not only firearms, but projectiles and casings related to a firearm and able to identify certain bullets or casings to a known firearm.

Scotland Yard CSI asks, how do we identify human remains?

Well, it depends on the state of the remains.

Crime scene investigators work with a medical examiner's office or a coroner's office to determine whether remains are human or not human.

Remains that are in an advanced state of decomposition to the point where they're skeletal, generally wanna work with an anthropologist.

They could tell you not only whether it's human or non-human, but what part of the body it came from, possibly the age or the sex of the person by looking at different bone growth markers.

And then sometimes looking at the damage to these bones could determine the cause and manner of death.

CXXIV001 asks, are we sure that every fingerprint is unique?

No, it's not possible to check every single one.

They're looking at whether it's a loop, it's a whirl, it's an arch.

But then really what they're using to identify is the minutia in your fingerprints.

Anytime you look at your fingerprint, that friction ridge split, it comes together, it starts, it stops, it ends, creates an island.

These are all points of identification that are to look at.

In the hundred plus years of analyzing and comparing fingerprints, they have yet to find two fingerprints that are identical.

GovNG asks, no seriously, does anyone know how to do a drugist fold?

A drugist fold or a pharmacy fold is a way to preserve small amounts of trace evidence in paper.

First thing you wanna do with your paper, you wanna fold it into thirds.

Fold it a third of the way in on both sides.

Then you wanna fold it into thirds again.

And then what you wind up if you open this up is you have nine equal sized boxes.

You would then collect your trace DNA and you put that trace DNA into the center square.

And then very carefully you wanna close that up, make a little point on one end, take this point, secure it into the pocket on the other end and now you have this little bindle now.

Then what you do is you would seal up this one end, put your signature across at the date and then this would be over packed into an evidence envelope.

From Chumi TM, if DNA could travel anywhere without us even being there, how reliable is DNA in forensics after all?

DNA analysis gets more sensitive as time moves on.

Technology gets better, it gets more sensitive.

There's different types of crime scene contamination and there's different types of DNA transfer.

Intra-crime scene contamination happens within the crime scene.

So if I touch this one object and I touch another object, I'm contaminating two different objects within the same scene.

Inter-crime scene contamination is contamination between two unrelated scenes.

I'm at a crime scene, I'm standing in blood, that blood is now drying on the soles of my shoes, I go to another unrelated crime scene, now that dry blood is starting to flake off into that crime scene, that's inter-crime scene contamination.

There's different types of DNA transference events that can happen.

We have primary, if I'm not wearing gloves and I touch a door handle, I'm transferring my skin cells to that door handle.

Secondary contamination would be if you and I shake hands and now I touch that door handle and I transfer your skin cells onto that door handle.

When they analyze the DNA, they could tell the difference between a major contributor and a minor contributor.

Analyst is not saying you shot that person, they're just saying that there's a presence of your DNA on that weapon.

Babyface16 asks, how in the fuck did OJ Simpson get acquitted?

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犯罪現場の捜査官だけど「科学捜査について」質問ある？ | Tech Support | WIRED Japan

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