Trace Evidence Ogle (2012) explained the importance of all types of trace evidence within chapter six of our textbook. Trace evidence are fibers like hair, clothing, or even soil that can be linked to something in turn leading to someone. Trace evidence have certain identifiable properties that allow investigators to follow leads and trails to hone in on a suspect and possible justice for a victim. Because of the importance of trace evidence, it is important that we review the importance of primary transfer, secondary transfer, and the importance of soil within a criminal investigation. In the beginning of our textbook Ogle (2012) introduced us to the Locard exchange principle which describes the theory that when two objects come into contact there would be a cross transfer of trace evidence such as hair, fiber, soil, etc. This is what the basis of primary transfer is. Secondary transfer is maintains the same principle however it goes a step further and refers to the subsequent transfer of trace evidence from the place to which it was transferred to in its primary transfer to another place or thing. Ogle (2012) give the following example: “… fibers transferred from a victim’s sweater to an assailant’s shirt can be subsequently transferred from the assailant’s shirt to the fabric of a chair that the assailant sits in, thus becoming a secondary transfer of the fibers.” (pg. 161)
Ogle (2012) not only applies importance to fabric and fibers being trace evidence but also the importance of collecting and tracing soil. According to Rogers (1992) the first use of soil in a criminal case was the murder of a strangled seamstress in October of 1904. A forensic scientist by the name of George Popp in Germany was asked to examine evidence in the case. He noticed the trace evidence and was able to track the primary and secondary transfers from a previous case and lead to one suspect, Karl Laubach who ultimately confessed. Because this person had been implicated in a previous case and the evidence was exact to the case Popp was examining they were able to put two and two together and determine who the offender was. Which brings me to my next point of the types of soil there are. This case would have never been solved if Popp hadn’t studied the different types of minerals found in different types of soil which is why it is important to know the three main grain sizes: sand, silt and clay. Bertini (2016) states the following ideas of the grain sizes of soil and their subcategories: “Sand has a gritty feel to it and it is composed of weathered rock. It is typically found by deserts, beaches or riverbeds. Silt on the other hand has a crumbly, slippery feel to it, similar to flour. It is mostly composed of medium sized mineral particles. You can find silt sediment in riverbeds. Clay, though, is sticky and it is composed of small particles adhering to each other and you can find this in various locations. There are three subcategories to soil which are peat, loam, and chalk. Peat has a compressible feel and is made up of decaying organic material. It is largely found in bogs, or areas where water is retained by organic matter falling to decompose. Loam is a loose feel and is made of a sand, silt, and clay mixture. Loam is best used for agriculture and can be found in various locations. Lastly is chalk although it can feel different depending on the chalk, you will normally see it in colors of white and brown. It is composed of alkaline soil with mineral stones and is found below the top soil.” Knowing these specific details within a crime scene would allow the investigator to know the path to follow in looking for the possible offender. Any secondary evidence left behind from soil on the victim that may have transferred from a shoe impression may also help identify or eliminate a suspect. Lastly, when discussing soil, we have to be able to know not only the different types of soil but what could be found in soil and where it is located within the soil. Take humus for example, you may think it is a tasty dipping snack but in the geology and forensic world humus is a form of mature compost (Klein, 1995). Although it is found in soil humus is not actually soil but it is most nutritious planting material around and is used to treat soil (Klein, 1995). According to Col (1996) humus is found in the top parts of soil. More specifically humus can be found in two different horizons of soil. For the most part Col (1996) says it is found in the O horizon but can also be found in the A horizon which is directly below the O horizon of the soil. It is found within these two horizons because the first two layers consist of predominantly decomposed organic material which is healthy for the other horizons of soil. When you know the different parts of trace evidence, specifically to soil, where the minerals can be found, and in what horizons you are more able to determine specific details within a case that can mean life or death for both the victim and the offender. Although it is highly important to find out details of hair, it is automatically traced by DNA therefore it is easier to find that type of trace evidence. However if you know the importance of soil in a crime scene that can just make you more knowledgeable of the crime scene and you will then be able to secure the correct areas so to not contaminate them. This will be most helpful within the investigation.

References
Bertino, A. J., & Bertino, P. N. (2016). Forensic science: Fundamentals & investigations. Boston, MA: Cengage Learning.
Klein, R. (1995). Humus Soil 101 | DoItYourself.com. Retrieved May 25, 2016, from http:// www.doityourself.com/stry/what-is-humus-soil#b
Ogle, Jr., Robert R. (2012). Crime Scene Investigation and Reconstruction, 3rd Edition. [VitalSource Bookshelf Online]. Retrieved from https://bookshelf.vitalsource.com/#/ books/9780133346510/
Rogers, J. D. (1992). Geoforensics Case Histories - J. David Rogers. Retrieved May 23, 2016, from http://web.mst.edu/~rogersda/forensic_geology/Geoforensics Case Histories.htm Col, Jeananda. Enchanted Learning. Soil - EnchantedLearning.com. (1996). Retrieved May 26, 2016, from http://www.enchantedlearning.com/geology/soil/