Abstract Physical evidence is what is collected after a crime has been committed. This evidence may be introduced into a trial. This would be the evidence that is collected that is from a non-living origin. There are many types of physical evidence that the investigators collect. This type of evidence can conceivably include all or part of any object.
The evidence that is found at the scene of a crime is considered evidence. One type of evidence that is found is physical evidence. This type can consist of fingerprints, footprints, handprints, tidemarks, cut marks, and tool marks. The Physical evidence is collected by the investigators and packaged and preserved by them as well. A few of the physical evidence that will be reviewed are; trace evidence, fingerprints, and footwear impression and tool marks.
The physical evidence known as trace evidence can be gunshot residue, paint residue, chemicals glass, and illicit drugs. When an investigator is gathering this evidence they may use tweezers, plastic containers that have lids, a knife, and a filtered vacuum device. With certain physical evidence they will need to use a biohazard kit. This kit will include disposable gloves, booties, face mask, a gown, and a biohazard waste bag.
If there was a gun used the investigators will need to collect the clothing of the victim and all others that may have been on the scene of the crime. This way the lab can check for gunshot residue. There could be gunshot residue on the victim which can indicate that it was a close shot. If there is gunshot residue on any of the others then it could lead to a suspect. The investigator will collect the clothing and put it all in sealed paper bags for the transportation.
If the investigators find illicit drugs or an unknown powder they will use a knife and then they will seal each sample that is retrieved in a separate sterile container. This will then be transported to the lab for them to identify the substance. The lab will also check the purity and see if there are any traces of anything else. The lab will determine whether there might be drug possession, drug tampering or if the substance could have killed or incapacitated the victim in anyway.
Fingerprinting is considered another type of physical evidence. This type of physical evidence is considered the most significant type of physical evidence in most crimes that an investigator collects. There are no two individuals that have ever been found to have the same fingerprints (Layton, J, 2011). An investigator will use certain tools to collect evidence. Those tools could be brushes, powders, tape, chemicals, lift cards, a magnifying glass, and super glue. The investigator will use the fingerprints to identify the victim and to identify or rule out a suspect. There are different types of prints that an investigator can find at the crime scene. They could be visible, molded, and latent.
The investigator will use powder for non-porous surfaces. The investigator will use a powder that contrasts most with the color of material that is holding the print. The surface will gently be brushed with the powder in a circular motion until the print is visible. It is then brushed in the direction of the print ridges. The investigator will then take a photo of the print and then afterwards there will be clear tape adhered to it so that it is lifted and placed on a fingerprint card (Layton, J, 2011).
Chemicals may also be used to lift prints. These chemicals are used for porous surfaces. The investigator will spray this chemical on the material or they may even dip this material into the chemical solution. This process will reveal the latent print for the investigator. An investigator may use super glue to retrieve the print. They do this by pouring the super glue onto a metal plate and then they heat it to around 120*F (Layton, J, 2011). The plate, heat source and the object containing the latent print are placed in an air tight container. The super glue causes fumes that will make the latent print visible to the investigator and it is not disturbing the material that it is on.
Impressions are other forms of physical evidence that the investigator will collect at a crime scene. A footwear impression can be left in the mud and a tool mark is usually left on the window or door frame. When the investigator cannot submit the entire footwear then they would need to make an impression to send to the crime lab. The investigator will make a casting of the footwear at the scene. This kit that the investigator may need to use would include multiple casting compounds, snow wax (which is used for a cast in the snow), a bowl, spatula, and a cardboard box (Layton, J, 2011).
The investigator will need to take a photo of the footwear impression in the mud first. Once the investigator has taken the photo then they can start to make the cast of the footwear impression. When making the cast the investigator will need to combine the casting material with water in a zip lock bag (Layton, J, 2011). They will need to knead this material for a few minutes until it is like pancake batter.
The investigator will then pour the mixture into the impression so that there are no air bubbles (Layton, J, 2011). This is to be poured until it overflows the impression. It is then left to set for about thirty minutes. The cast is carefully lifted out of the mud. The investigator does not try to clean the cast before placing it into the cardboard box and sending it to the lab.
Then there are the tool mark impressions that an investigator will collect for evidence. These are harder for the investigator to use compared to the footwear impression. When the investigator does not have the ability to transport the item containing the tool mark then the investigator will make a cast of it. An investigator has two types of tool marks that they may find at a crime scene. Those marks can be impressed or striated (Layton, J, 2011).
The impressed is where there is a hard object that makes contact with a softer object, but it does not move back and forth. This would be like the marking of a hammer on a door frame. This is where the impression of whatever tool is used is left on the softer object. The striated impression would be where there is a hard abject that is making contact on a softer object which moves back and forth (Layton, J, 2011). This would be like the pry marks that are left on the window frame. These impression are parallel line impressions.
References Enotes. (2011). Physical Evidence. Retrieved from http://www.enotes.com/forensic-science/physical-evidence Layton, J. (2011). How Crime Scene Investigation Works. Retrieved from http://science.howstuffworks.com/csi4.htm