Trace Evidence

Trace Evidence

Crime scenes are known to have many clues left behind. The obvious would be a the body or bodies, clothing, and sometimes even the murder weapon. While these are great way to solve a case there's another kind of evidence; trace evidence. Trace evidence are small pieces of evidence that are laying around a crime scene. There are many types of trace evidence some of them include metal filings, plastic fragments, gunshot residue, glass fragments, feathers, food stains, building materials, lubricants, fingernail scrapings, pollens and spores, cosmetics, chemicals, paper fibers and sawdust, human and animal hairs, plant and vegetable fibers, blood and other body fluids, asphalt or tar, vegetable fats and oils, dusts and other airborne particles, insulation, textile fibers, soot, soils and mineral grains, and explosive residues. Although these are the most common found elements, they are not the only ones. The Trace Evidence Unit is known to examine the largest variety of evidence types and used the biggest range of analytical methods of any unit. materials are compared with standards or knowns samples to determine whether or not they share any common characteristics. In this paper I will discuss the different kinds of trace evidence and how crime scene investigaros use it to solve cases and convict criminal.

Trace evidence was first discovered by Edmond Locard. Edmond Locard was born in 1877, and founded the Institute of Lyon’s Institute of Criminalistics. He is also known for advancing the science of fingerprints. In 1910 he was authorized to start a small forensic laboratory in the Palais de Justice which he directed until 1951.While there he worked on criminal identification methods including poroscopy- the microscopic examination of fingerprints; analyses of body fluids, hair and skin; and graphometry or handwriting analysis. He is the man responsible for coming up with the theory that when two objects come in contact with each other they leave some kind of material matter behind. This theory was later called Locard’s Exchange Principle. The idea is that the evidence can be used to associate objects, individuals or locations with one another." A person typically loses about 100 hairs a day. These hairs may be of evidentiary value to show contact between two people. With an adequate hair standard, a trace chemist will be able to microscopically compare an unknown hair to a standard collection and determine if the unknown hair could have come from the individual under investigation. Hair comparisons can not identify a hair as coming from one individual to the exclusion of anyone else. DNA testing can strengthen any possible association of the hairs." - Locard.

Hair is usually found in unusual amounts when there was a struggle or fight between the victim and suspect or suspects. Hair at a crime scene is usually found on the floor near whatever was used to commit the crime or the point of impact between the suspect and victim. If a hair is found with the root still intact then DNA can be pulled from it although DNA can also be found from fingernails, toenails, and skin flakes. Hair can tell the investigators many things. For insance, the race of the person, whether they dye their hair or not, the natural color of their hair, and if it simply fell out or a lot

of force was used to pull it out of the scalp.

Fibers are found mostly on clothing, furniture, carpeting, and blankets at a crime scene. The fibers found are usually from either clothing or carpet. Cross-transfer of fiber evidence usually occurs where person-to-person contact was established. There are well over a thousand known fibers and a few thousand known dye formulas. Every dye formula is registered and available in the database investigators use to compare these small pieces of evidence.

Glass from doors, decorations, or windows are usually found on clothing and the soles of shoes. It can also be found on tools, skin, and even the weapon. Different types of glass break and shatter differently as well as have different characteristics when it comes to densities and refractive indexes. Glass can also hold fingerprints which can be very valuable to an investigation as the fingerprints can be taken up on tape and then ran through a database, possibly finding a match and allowing the investigators to find and capture a suspect.

Weapons, pray bars, blunt objects, clothing, and shoes are where paint chips from door, walls, and furniture can be found. In order for paint to chip off there needs to be a pretty serious struggle or a pretty hard force that will chip away at the paint then causing it to land somewhere that the suspect forgot about. The Crime Scene labs have about forty thousand different types of paint in their database. The majority of paint chips are from hit and run cases involving automobiles.

Dust and Dirt can determine many things to