Hair and Fiber

Hair and fibers are usually the most abundant evidence at a crime scene, but often go unnoticed. When there aren’t any prints, hair and fiber are a crime scene investigators greatest ally.

Fibers are very transferable and are now commonly used to link a suspect to a crime. They can be classified into two categories, natural and man-made. Natural fibers are things like wool and cotton, while man-made fibers are things like polyester and nylon. By taking cross sections of fibers and putting it under a microscope are able to determine what the fiber is, who manufactured it and where it came from.

Hair is also common at a crime scene and by looking at a hair under a microscope a forensics specialist can see evidence of drug use, they can tell what animal the hair is from, they can determine the ethnicity of the person among many other things. They do this by identifying and classifying the shaft, medulla and cuticle of the hair.

Hair and fiber may seem insignificant, but in fact are some of the most important evidence at a crime scene.

Sources:
http://stereoscope.com/?p=3
http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric3.htm

Hair and Fiber Pictures

Color Treated Hair

Thin, possible blonde shaft.

Difficult to see.

African American

Brown shaft, black medulla.

Asian Hair

Cut end, brown shaft, black medulla.

White Male Hair

Purple shaft. Wide, gold medulla.

Cat Hair

Stacked appearance, frayed cuticle, dark shaft.

Classified as coronal.

Dog Hair

Clear shaft with dark medulla.

Also was the unknown hair.

Synthetic Hair

Thready appearence, brown shaft.

Source:

Pictures from Olivia's blog

http://www.okretschmerforensics.blogspot.com/

Blood Type

There are four major types of blood groups: A, B, AB, and O. Although there are only four major blood types there are subclasses which come into effect during blood transfusions. Blood transfusion is the transfer of blood from one person to another and occurs after major blood loss. The reason behind it is your body can’t produce enough blood fast enough and therefore your body can’t oxygenate it’s self, so blood is transferred intravenously through an IV drip to replace the lost blood and oxygenate your body. The major blood types can each be broken down into two subclasses based on the absence or presence of protein, making it either positive (+) or negative (-). This is called the Rhesus factor; if protein is present in the blood it is Rh positive and if protein is absent than it is Rh negative. For a successful transfusion to occur the same blood type with the correct Rh factor is needed or else a hemolytic transfusion will occur, which results in your immune system attacking the transfused blood cells and your blood will agglutinate (clump together). This is why usually O blood is transferred because it doesn’t have any antigens causing it to be accepted by the immune system regardless of blood type, which is why it is called the universal donor.

In the blood type lab we tested the blood types for A and B antigens by taking two samples of each blood type and adding A antigen to one sample and B antigen to the other. After mixing the sample with the antigen if the blood was grainy then it was positive for that antigen and if it was gelatinous it was negative for that antigen. This chart represents our findings.

Sources:
http://www.fi.edu/learn/heart/blood/rh.html
http://nobelprize.org/educational_games/medicine/landsteiner/readmore.html
http://health.yahoo.com/blood-treatment/blood-transfusion/healthwise--tc4111.html
http://www.nhlbi.nih.gov/health/dci/Diseases/bt/bt_whatis.html Picture: http://healthcareblog.experience.com/2008_04_01_archive.html http://schools-wikipedia.org/wp/a/ABO_blood_group_system.htm

Final Investigation

Purpose: To investigate and solve a crime using forensic analysis techniques learned in class.
Crime: Robbery.

Investigation:
When we arrived at the scene there were six pieces of evidence (a wallet, a beaker with a fingerprint, a ransom note, blood, and two types of hair) and eight possible suspects. We identified the wallet found at the scene as Mike Kelly's suggesting he was either robbed or was involved in the crime. There was a beaker next to the wallet with a ulnar loop like Mike Kelly's fingerprints. We checked his records and found he's an educator. Also there was a ransom note in an envelope that read "I have your diamond ring". The hand writing matched Ralph Nelson's hand writing. With this new information we could rule out Mike as a suspect. Next we found blood near the beaker, suggesting a struggle. The blood type was A which matched Jenny Cho's, a chemical engineer, and Ralph Nelson's, a college professor. Also present was Asian or African American and Caucasian hair, placing Jenny Cho and confirming Ralph Nelson's and Mike Kelly's presence at the scene. Upon looking at Jenny Cho's records we found she had a prior arrest for petty theft in '88.

Summation:

Taking into account all the evidence, here's what happened Jenny Cho had been having an affair with Mike Kelly behind Ralph Nelson's back. When Mike proposed to Jenny she decided to leave Ralph. Ralph became angered and wrote Mike a note to lure him out. When they met they fought and during the struggle some of Mike's hair fell out and either Jenny's hair transferred from Ralph or some of Ralph's hair fell out. Also during the struggle Mike dropped the note and his wallet fell out his jacket. Mike then took out a beaker and hit Ralph causing him to bleed. Seeing Ralph unconscious Mike ran away and Jenny Cho came upon Ralph and helped get away, but not before she took the money from Mike wallet.

Pictures: http://www.okretschmerforensics.blogspot.com/