Hair Analysis Essay
To start off I will talk about the structure of the hair. First, we have the medulla. The medulla is the innermost layer of the hair shaft. It is the center. Forensic investigators classify hair into five different groups depending on the appearance of the medulla. Next we have the cortex. The Cortex is the largest part of the hair shaft. It also contains the most pigment. Finally we have the cuticle, which is a transparent outer layer of the hair shaft. It looks like scales almost. The cuticle can be used in order to analyze the hair for different toxins, drugs, or metals at specific points in times. It is also used to determine whether the hair is animal or human.
There are many different types of medulla patterns. Continuous is one unbroken line of color while interrupted is broken at intervals. Fragmented are when the pigmented lines are unevenly spaced. Solid are when the medulla and the cortex are both pigment filled. None is when there is no separate pigmentation in the medulla. There are also 3 different types of cuticle: imbricate (look like lines, almost like a wall going up), coronal (stacks), spinous (horizontal layers).
Other important terms related to hair are: keratin (type of fibrous that make up the majority of the cortex of a hair), melanin granules (bits of pigment found in the cortex), hair follicles (the actively growing root of hair).
There is also microscopic variation in hair. The medullary index measures the diameter of the medulla relative to the diameter of the hair shaft. This helps distinguish animal hair from human hair. As said before, there are 3 different types of cuticules (imbricate, coronal, and stacks), which can help narrow down suspects.
Cortex color determines the color of the hair, so forensic scientists can determine the color of someones hair with one strand. The diameter of hair can also be determined microscopically and can help the scientist know how thick the suspect’s hair is. Also, once again, it helps determine if the hair is human or not (medullary index, if the number is high it is probably animal).
Now, I will convince the jury why I believe suspect number 1 is the offender. Hair is class evidence, it helps us eliminate different suspects. Now, although hair might be at the crime scene prior to the investigation, it is still highly unlikely that these multiple strands were there. Our investigators found clues of a struggle, which would explain why there was a lot of hair left over. Upon examining the hair, the medulla type found at the scene was a continuous medulla pattern.
Only suspects 1 and 2 have a continuous medulla pattern, suspects 3, 4 and 5 have either no medulla or a fragmented medulla. Because of this, our suspect class goes down from 5 suspects to 2 suspects. The next clues we found with hair is the medullary index and cuticle. While both suspects have the same pigment color, they do not have the same hair thickness (medullary index) or cuticle. The hair at the crime scene has a medullary index and a cuticlethat matches suspect 1, not suspect 2, so it allows us to give us the assumption that it is suspect A.
In summary, by examining the hair we were able to shrink down our class (hair is class evidence) and eventually narrow it down to a suspect. By looking at the medulla, we were able to narrow down the suspects to those with a continuous medulla. Finally, after examining the medullary index and type of cuticle, we found that suspect 1 matched with the hair at the crime scene in terms of the hair thickness and cuticle.
In conclusion, now that you know all about the structure of the hair, the variation of the hair’s medulla and cuticle, we can narrow down the suspects to a class that has a continuous medulla, a medullary index that matches the one at the crime scene, and a cuticle type that was found at the crime scene.