H.W. “Rus” Ruslander
MS. CSCSA, CLPE, D-ABMDI & CBPE
Use Gun Bluing….As An Aid to Investigations
With increasing frequency, the crime scene investigator, processing
a scene, comes across fired cartridge casings. It is of the utmost
importance to process these casings for latent fingerprints in
order to assist in the identification of the perpetrator.
Develop latent fingerprints on
brass cartridge casings recovered
from crime scenes is an added step in helping identify the
Recovered casings can be dipped
into diluted or undiluted gun
bluing to cause a chemical reaction
between the bluing and the fingerprint residue on the casing.
It seems to work best on brass
casings not the nickel plated
or aluminum types.
The reaction is fast and must
be stopped with a water bath
before the print is overexposed.
Other Processes Can Be Used
- Super Glue Cyanoacrylate
- Fixes Latent Prints to Surface
- Prevents Latent From Being Damaged
- Works Well, Gives Good Results
Eye, Hand & Respiration
in Well Ventilated Area
Before you ever Process Real Evidence
- Practice on similar items in the lab.
- Document your procedures and results.
- Keep a log of what you do for future reference.
- Take basic and advanced training courses.
- Discuss techniques with co-workers.
- Be comfortable with the procedure.
Take Special Note
- Are the shell casings all the same caliber?
- Are they the same brand?
- Are they the same color?
- Color is described as white metal or yellow metal.
- What color
is the primer?
- What is the head stamp information?
More on Processing
- If using Gun Bluing, NEVER dip
the base in the bluing.
- Have a fresh water dip tray readily available.
- Watch the
reaction very closely.
- It only takes a few seconds to occur.
- You can always re-apply if the reaction is too weak.
photograph any results
- Remember depth of field, this is a curved surface.
Mixing the Gun Bluing
- Can be used either full strength or diluted
- 50:50 is best
- Half gun bluing and half distilled water
- Causes reaction to slow down
- Easier to control
- Try various
- Use the mixture you are most comfortable with
Steps to Take
- First, you must use tweezers, terminal pliers or forceps that
will not react with the bluing. Use either plastic tools or
dip metal ones in the liquid plastic sold in hardware stores.
- Grasp casing by base, not neck.
- This protects the primer from becoming altered by the acid.
- Dip quickly and remove. Watch closely!
- Watch the reaction closely; it only takes a few seconds.
- If you wait too long, the casing will turn black.
- Immediately dip the casing in fresh water to stop the reaction.
- Examine the results.
- If reaction is not acceptable, repeat process but watch it
- Metallic objects