Archive for February, 2008
Latent fingerprints are nearly invisble to the naked eye. They’re left when someone touches an object, leaving behind sweat and oils. Detectives make the print images visible by using powder that clings to the oily ridges of the fingerprint.
All police officers are trained to use basic fingerprinting equipment – brushes, powders, tape, and lifters.
Basic fingerprinting kit.
Investigators use brushes to apply print powder. The best brushes are made from the feathers of a maribou, a member of the stork family. A second type brush – camel hair – is also an excellent brush. Interestingly, camel hair brushes are not made from the hair of actual camels. Instead they’re made from the hair of small mammels, such as rabbits and squirrels. Synthetic brushes are widely used because they’re less expensive than the other types.
Maribou feather brush
After a print has been developed, the detective uses tape that’s similar to wide packing tape to lift the print from the surface. She then presses the tape and captured fingerprint against a white card creating a permanent piece of evidence.
Another great tool – my personal favorite – for lifting prints is a hinged fingerprint lifter. The front of the lifter is a small square of tape. The second part of the lifter is a white backing. The print is lifted with the tape which is then pressed tightly against the backing to preserve the fingerprint. Lifters come with pre-printed spaces for the date, time, officers initials, and case numbers.
Hinged fingerprint lifter.
* All photographs courtesy of my friends at Sirchie Finger Print Laboratory
* Notice – The Graveyard Shift is pleased to announce a special guest blogger on Monday 3-3-08. Sgt. John Howsden (ret.), a thirty year veteran police officer, will be discussing body armor (Kevlar vests). Stop by and pick his brain. As usual, we’ll have some cool photographs. One is really cool.
* Fingerprinting will continue next week. Be prepared to take lots of notes.
Detectives use a variety of means to collect crime scene evidence. When attempting to locate evidence, investigators must be methodical. One way to be certain they’ve combed every inch of a crime scene is to conduct structured, patterned searches, such as spiral or grid searches.
Spiral search patterns are an effective means of locating evidence.
Grid search patterns are especially effective when searching large areas, such as a field or other open land areas. Each grid block is assigned a number or letter. Detectives use those identifiers as reference points when testifying in court. Example: “I located the murder weapon in block number 4. I also discovered spent bullet casings in block number 3.”
Alternate light sources (ALS) are useful when attempting to locate hard-to-see evidence, such as fingerprints and body fluids. Devices such as Sirchie Fingerprint Laboratory’s Krime Site Imager are invaluable for detecting and capturing fingerprint images. The KS Imager is battery operated and is capable of recording images in bright light or in total darkness.
All too often, fingerprints are destroyed during crime-scene processing (dusting and lifting prints) Using a device such as the KS Imager allows investigators the opportunity to photograph a perfect image of a fingerprint before attempting dust and lift it. Therefore, even if the print is marred, detectives will still have perfect image of the print, an image that’s permissible as evidence.
A detective uses a Krime Site Imager to locate and photograph fingerprint evidence.
Some crime scenes, such as labs used for manufacturing methamphetamine, contain hazardous materials, such as flammable and toxic chemicals and fumes. When searching those dangerous crime scenes, investigators must wear protective gear and clothing.
A detective wearing a hazmat suit gathers evidence from a meth lab.