Combination rifle and shotgun

 

Rifling is the term used to describe the twisting pattern of grooves and lands (raised areas between grooves). Lands and grooves are tooled into steel gun barrels to cause the projectiles (bullets) to spin. The spinning movement stabilizes the bullet, causing it to travel straight and true, sort of like how a football spins when thrown by a quarterback.

Gun barrels start out as solid pieces of steel.The center hole is cut using a drill. Then, the rifling pattern is tooled to the inside of the barrel.

A tool, such as the one pictured above, is forced inside a newly drilled gun barrel, cutting lands and grooves as it passes through.

When a barrel is manufactured, marks caused by contact with machinery are left in the steel. These blemishes are different on each barrel, causing individual guns to have distinguishable fingerprints. No two set of markings are the same. Also, normal use of a firearm can cause distinctive markings inside the barrel.

Bullets are made from soft metal, such as lead. As they pass through a rifled barrel, the imprint of lands, grooves, and tooling blemishes are permanently stamped into the projectile.

Investigators use each of these markings to match bullets with the gun that fired them.

 

Spiral pattern of lands and grooves

 

Bullet with impressed image of lands and grooves in its surface

Gun stuff for fun…

Caught by surprise

 

Better prepared

 

Don’t monkey with me.

 

No way I’m hunting with Dick Cheney.

 

I told you I’m sick of canned food. I want real fish, and I want it NOW!

For those of you who couldn’t make it, Forensic University hosted a day at the gun range for members of Sisters in Crime.

The new Bond.

* BREAKING NEWS *

POLICE PROCEDURE AND INVESTIGATION has been nominated for a prestigious Macavity Award! I’m truly thrilled and humbled to be included with such a star-studded group of authors. What an incredible honor. Thanks so much!

Fingerprinting

 

The process of fingerprint fuming is relatively easy. All that’s needed to perform the technique is a fairly airtight tank, some heat, and a few drops of Superglue.

Fingerprints leave behind traces of amino acids, fatty acids, and proteins. Those ingredients, combined with the moisture that’s found naturally in the air, react to the fumes produced when Superglue is heated. That reaction forms a sticky, white material that clings to the ridges of fingerprints, making them visible.

Detectives take photographs of the chemically developed prints for entry into AFIS and for use as evidence in court.

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Detectives use the same glues found in retail stores for use in fuming chambers.

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CynoSafe Fuming Chamber

Items to be printed are placed inside an air tight fuming chamber, such as Sirchie Fingerprint Laboratory’s CyanoSafe. A few drops of Superglue are placed into a heating tray inside the chamber. The glue is heated which releases its vapors into the air. The CyanoSafe is designed to provide the ideal humidity level for the development of fingerprints.

The machine automatically purges the fume-laden air from inside the chamber after the process is complete. Tabletop models, like the one pictured above can cost anywhere from five-thousand to ten-thousand dollars. There are portable units available that’re made from heavy plastic. These units are collapsable for transporting to a crime scene. The costs for the portable units start at around one-hundred-fifty dollars.

Fingerprint developed using Superglue

In many cases, officers don’t have the necessary resources available to conduct their own print development; therefore, they must send the items they’d like printed to an outside laboratory. As a result, prints are often destroyed or wiped away during the trip to the lab. To reduce the risk of destroying a print, it should be fumed – preserving the print – prior to placing the item in a package for the trip. Without the proper equipment, this is impossible.

* Many police departments do not have the funds to buy expensive fuming equipment; therefore, detectives are sometimes forced to become a bit innovative by making their own crude fuming chambers out of glass aquariums, Rubbermaid bins, and even cardboard boxes lined with aluminum foil. Costs – a few dollars. Results – same. Danger to detectives from toxic fumes and burns – high.

Maybe writers should adopt a needy police department, take up a collection, and purchase them a nice fuming chamber.

FYI – Here’s a link to an interesting article on The Boston Channel. It about stupid crooks cutting off their fingerprints to avoid jail time.

http://www.thebostonchannel.com/news/15478914/detail.html

If the Shoe Fits

Detectives look pretty darn silly walking into court carrying a pair of plaster footprints. But, footprint and tire impressions can be extremely helpful to an investigator’s case. They’re especially helpful when the casts are a perfect match to the shoes the defendant chose to wear to the hearing. Yep, that’s actually happened.

Collecting impression evidence isn’t all that difficult, even in mud and snow, if you’ve got the proper tools. Here’s a look at the process of collecting footprint evidence.

Investigators usually keep an impression casting kit in the trunk of their police car.

Impression casting kits contain a casting material that’s similar in composition to the material dentists use when making impression molds for dentures.  The kits also contain dust, dirt, and snow hardener.

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Dust and dirt hardener firms up loose soil.

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Snow impression wax prevents snow from melting during the casting procedure.

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Casting powder is mixed with water and then poured directly into the impression.

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Hardened cast of suspect’s footprint.  The cast is used to identify a suspect’s shoes by size and unique characteristics, like cuts and indentations.  The cast also becomes part of the evidence that’s used in court.