Forensic Tips

Useful, common-sense, and innovative forensic tips.

 

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Every day, forensic scientists and crime-scene investigators find ways to get their jobs done faster and easier. Here, we have compiled some reader-contributed forensic tips. Feel free to try these tips—and then send us some of your own ideas.

Important note: As with any forensic technique, you should be certain to experiment and practice on staged items before trying any of these tips on real evidence. And always follow your agency’s standard operating procedures and protocol.


Magnifying glass stand-in

If you find yourself in the field without a magnifying glass, here is a workable alternative: Just hold a pair of binoculars upside down and put the eyepiece near the item that you need to examine. Look through the other end—and you will find that binoculars can work fairly well for magnifying objects that are up close, too!

— From Chris Kemp
Park Ranger
Sacramento County Regional Parks
Sacramento, California


Hard-to-read serial numbers

When the serial number or the ID stamp on a firearm is difficult to read, try these simple steps:

  • Thoroughly clean and dry the area.
  • Apply powder chalk in a contrasting color. (Powder chalk can be purchased at any hardware store. It is used for chalk lines.
  • Use an alcohol wipe to remove the excess.
  • Vary the lighting for photographic documentations.

— From Clare Wallis
Chief Gunsmith
JCW International
Houston, Texas


Document your prints

After you process a piece of paper for fingerprints with Ninhydrin, take the paper to the copier and make a copy. The fingerprints will be dark, crisp, and permanent.

—From Det. Greg Wise
Hohenwald Police Department
Hohenwald, Tennessee


Resizing many photos at once

If you frequently find yourself resizing large batches of images, you may want to try downloading Microsoft’s free Image Resizer. This software allows you to resize an entire folder’s worth of photos at once. The software leaves the original photos untouched, but provides you with smaller versions that are easier to e-mail or share.

—From Det. Joshua Shelton
Criminal Investigations Division
Fayette County Sheriff’s Office
Fayette County, Georgia


Revealing oily footprints

Here was the problem: A suspect at a gas-station burglary stepped in clear motor oil, and then he stepped onto a Plexiglas light fixture. Lieutenant Colonel Jeffery W. Hart could see the resulting footprint, but photography did not reveal any detail. He was concerned that brushing fingerprint powder onto the impression would cause the print to smear and would also ruin the brush.

His solution: Hart placed black fingerprint powder into an atomizer and sprayed a small amount of black powder into the air, letting it settle in a light layer onto the oily print. He then used a can of compressed air to remove the excess powder. The impression was lifted with clear contact paper and placed on a sheet of white paper.

“This lift, tied with a field interview by the third-shift officer of a person on the lot, resulted in a confession and arrest,” reported Hart.

—From Lt. Col. Jeffery W. Hart
Morganfield Police Department
Morganfield, Kentucky


Photography through microscopes

Photographing evidence through microscopes is a very important part of the documentation process, but many agencies cannot afford to purchase the proper connections that allow them to take digital photographs directly through a microscope.

Here is a solution devised by Salvatore Bianca, an analyst with the Maryland State Police Trace Evidence Section:

Place a cardboard toilet-paper tube over the ocular. The tube can be cut down to accommodate any brand of digital camera, different zoom capabilities, and various microscopes. This technique will work with both stereo and compound microscopes.

“If, for some reason, the tube gets bent, cut too short, or contaminated, it is easy and inexpensive to replace,” said Sandra Hartsock, forensic scientist supervisor at the lab. “And we always keep extra tubes on hand.”

—From Sandra Hartsock
Forensic Scientist Supervisor
Trace Evidence Section
Maryland State Police
Pikesville, Maryland


Photocopy your hard drive (literally)

When examining hard drives as evidence, accurate notes are important. But it can be easy to make a mistake when transcribing the long serial numbers into your notes. Detective Joshua Shelton suggests placing the suspect hard drive on the copy machine and making a copy of its label. You can then use that copy to keep notes about the case (case number, times, agents’ names, etc.), and you can be certain the serial number is correct and that your notes correspond to the correct hard drive.

—From Det. Joshua Shelton
Criminal Investigations Division
Fayette County Sheriff’s Office
Fayette County, Georgia


Watch for blood blowback

When a firearm is discharged in contact with or in close proximity to a victim, blood blowback may be found in the bore of the rifle, pistol, or shotgun. This is because the vacuum caused by the passing projectile sucks blood into the bore. Bad guys know to wipe down the outside of the firearm, but the phenomenon of blood blowback is not common knowledge.

A borescope equipped with a 90-degree mirror tube can help examiners determine the presence or absence of blood blowback in the bore. Test-firing without first doing a careful borescope inspection could destroy valuable DNA evidence.

—From Ken Harrington
Market Manager - Shooting
Gradient Lens Corporation
Rochester, New York


Cross polarization in forensic photography

Cross polarization is a technique used to capture back-scattered light from a subject while dramatically reducing or eliminating direct planar light that is reflecting from a subject, and is primarily used in nature photography. This technique allows a photographer to reduce or eliminate glare caused by flash commonly observed on oily, waxy, wet, or otherwise shiny surfaces.

Application in forensic photography would be when photo-graphing injuries on oily or sweaty skin, latent prints developed on shiny surfaces, patent prints developed in any shiny or oily medium, or any subject through glass. Cross polarization is particularly suited for autopsy photos.

This technique does not require a great deal of equipment. Aside from the camera and flash unit, a circular polarizer (attached to the camera lens) and a linear polarizing filter (attached over the flash) are required. A sheet of linear polarizing acetate (readily available from various scientific supply houses) can be cut to fit the flash head. If using more than one flash, be certain that you orient the linear polarizing acetate in the same direction on both flash heads.

Cross polarization of the camera filter and flash can be established by holding a piece of linear polarizing acetate in front of the camera lens, oriented in the same direction as the acetate over the flash heads. Turn the circular polarizing filter until maximum darkness is observed.

Best results are achieved when the camera filter’s orientation is 90 degrees (perpendicular) to the flash filter’s orientation. For future reference, a mark can be made on the circular polarizer rings.

Through-the-lens metering can compensate for the circular polarizing filter on the camera. However, exposure value on the flash unit should be increased 2 to 3 stops to compensate for the filter over the flash head. For greater accuracy, a light meter can be used to determine the stop adjustment. Flash range can be significantly reduced by use of this technique with low-power flash units.

—From Ptl. George D. Potash
Columbia Police Department
Columbia, South Carolina


Get prints from spots you can’t see

For example: The backs of car door handles, refrigerator handles, or door bars on buildings. They can all be good places to look for latent prints—but they can also be difficult to see and maneuver in order to process and recover those prints. Gail Mills suggests this technique:

  • Process the backside of the handles with fingerprint powder.
  • Use a swivel-head mirror and flashlight to see where the developed prints are located.
  • Mark the area with a dry-erase marker to indicate the location of the latent prints.
  • Place a piece of fingerprint tape on a craft stick or a tongue depressor. This will keep the tape rigid and make it easier to control the tape when placing it behind the item and maneuvering it onto the print.

Note: Smaller pieces of tape work better than large ones, as the removal of the tape from the item can be tricky.

—From K. G. “Gail” Mills, CSCSA
Crime Scene Investigator
Special Investigations Division
Criminal Investigations Bureau
Harris County Sheriff’s Office
Houston, Texas


How to flatten a plastic bag

Plastic bags are routinely submitted as evidence and examined for latent prints. Often, however, those bags have creases, folds, or are simply crumpled. When a latent print develops on the bag, it can be nearly impossible to photograph the print in its entirety. One simple solution is to use wooden embroidery hoops to flatten out the bag, allowing the developed latent to be photographed on a single, flat surface.

—From Andrew Reitnauer, MSFE, CCSA, CPO
Criminalist II
Crime Laboratory
New York Police Department
New York, New York


Sticky situation

A couple of enterprising criminals began placing rodent glue traps inside the drop-boxes at several apartment-complex offices. The residents’ rent checks stuck to the glue traps when they were pushed through the slot. The perpetrators would return in the morning and retrieve the traps (and the checks). They then cashed the checks using forged IDs.

Eventually, one of the glue traps came loose, fell into the office, and could not be retrieved by the perpetrators. Their fingerprints were “beautifully” stuck in the glue, said Detective Ken Kraus—but the glue is made of a non-drying, strong, sticky gel-like substance.

“We made several telephone calls to different laboratories and agencies to ascertain how best to preserve the prints,” said Kraus. “Unfortunately, nobody had an idea.”

So Kraus and his colleagues went to the hardware store, bought some glue traps, and began experimenting with their own fingerprints back at the lab.

“After several failed attempts to capture and lift the prints with cyanoacrylate, SPR, and even powder, we settled on spraying a very fine mist of Aqua Net hairspray into the air and letting it fall onto the glue trap,” said Kraus. He emphasized that the hairspray should be sprayed into the air and allowed to fall indirectly onto the print. The application of too much spray will fill in the ridges and furrows of the impression.

The hairspray dried “sort of like a polymer,” and the print was placed into a clear petri dish for evidence storage. It was later fluoresced with Ardrox, which worked well under UV light so they could photograph the prints and run them on their AFIS.

The perpetrator was identified and warrants issued.

—From Det. Ken Kraus
Roswell Police Department
Roswell, Georgia


NOTE: All of the following tips are from H.W. "Rus" Ruslander
CSCSA, CLPE, CBPE, CEP, D-ABMDI
Chief Investigator
Palm Beach County Medical Examiner's Office
West Palm Beach, Florida

The eraser trick

Once you develop a latent print with fingerprint powder and apply the tape, try applying a retractable, refillable, extra-long eraser to the tape. Rub it back and forth on the tape in at least two different directions. This presses down the tape into the nooks and crannies of the surface and results in a much better lift.

The popsicle pusher-upper
shell-casing holder

When you buy the treat usually called a “pop-up”, save the plastic pusher-upper. You can invert this little object and put it inside your superglue fuming chamber, slide a cartridge casing down over it, and start gluing. This will keep the casing off the bottom of the tank and allow the glue fumes to circulate all around.

Magnetic photo scales

Go to an office-supply store and buy a pack of magnets made for mounting business cards. Cut the magnets in strips and stick them to the back of the photo scales you already have. Now they will stick to metal—like cars, for example.

How to dust an overhead
horizontal surface for latents?

Try camphor. Go to your local pharmacy and buy some camphor sticks.

  • Put one on a metal surface—such as a paint-can lid—then light it, and watch the black, sooty smoke pour off it onto the overhead surface.
  • Keep moving it back and forth over the area you want to process.
  • When finished, take a fingerprint brush and gently brush away the excess soot. What you have left is a print ready for lifting with tape.

Need a camera boom?

Go to your local home-repair warehouse and buy an extension handle for painters. They come in either plastic or metal. Get a few PVC caps and a threaded gooseneck and screw it onto the end of the handle. Drill a 5/16-inch hole in the cap. Insert a 1/4-20 bolt and epoxy it into the cap. Screw the cap onto the end of the goose-neck. There you are: an extension handle that you can mount your camera on and extend up or over the scene for perfect look-down photos.

The chalk-line grid

When doing blood-spatter interpretations, instead of laying out scales across and up the wall, a new method is to grid out the area directly on the affected wall. To do this, create a grid on the wall in one-foot squares. Using a chalk line, you can easily snap the lines into place. If you buy any of the different colored chalks now available, achieving a contrast with the wall color should be no problem.

Do some simple math

Accurate measurements are important when documenting any crime scene. When measuring to a point from a baseline or a wall, it is necessary to ensure that the measuring device is 90 degrees from the baseline. An easy way to maintain and confirm this 90 degree angle is the 3-4-5 method used in construction framing: Measure out 3 inches from the point where the device intersects with the baseline, and measure up 4 inches from the baseline. The distance between those two points must be 5 inches if the angle is 90 degrees. (Visualize a right triangle with the 30 degree, 60 degree, and 90 degree corners.)

Chopsticks anyone?

Even though I can’t seem to master the art of eating with chopsticks, every time I eat at a Chinese restaurant, I ask for a set. I keep them and add them to my crime-scene kit. When necessary, I can pull out a set and use them to probe bullet holes, clotted blood, or any other area where I wouldn’t put my hands or where I cannot reach. The wood of the chopsticks is soft enough to prevent them from damaging projectiles, shell casings, or any other object I may be probing for.

Is a handgun loaded or not?

Using caution, you can take one of the previously mentioned chopsticks (see “Chopsticks anyone?” above), gently slide it down the barrel of the weapon, and slide your fingers down it until they come in contact with the end of the barrel. Keeping a grip on the chopstick without moving your fingers, remove it from the barrel and lay it along the top of the barrel or action and compare where the end of the stick comes in relation to the end of the chamber. If it comes to the bolt face, the weapon is unloaded.

Which way does it turn?

An easy way to determine the direction of cylinder rotation on a revolver, without pulling the trigger, is to look at the notch on the cylinder stop. This is located on the side of the cylinder toward the rear. The sloping notch is like the arrow indicating direction. The direction it faces is the direction of rotation. For example, if it faces toward the left, the rotation is clockwise; if it faces toward the right, the rotation would be counterclockwise.

Where did the bullet come from?

When a bullet strikes a piece of glass—such as a windshield—at an angle, it usually ricochets off. If you look at the ricochet, it looks similar to a teardrop. The sharp edge or rounded end is where the bullet first struck the surface. The pointed end points in the direction that the bullet was traveling. Bullets that ricochet off glass or other non-yielding, smooth surfaces at low angles will leave a tail indicating the direction of rotation. In cases where there were multiple guns fired, the direction of rotation could help indicate from which gun the ricocheted bullet came.

Non-stick casts

When using commercially available forms for casting impressions, spray the inside of them with a non-stick cooking spray prior to use. This will prevent the casting material from sticking to them.


ORIGINALLY PUBLISHED:
"Forensic Tips," written by Multiple Authors
September-October 2010 (Volume 8, Number 5)
Evidence Technology Magazine
Buy Back Issue

 
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