Biological Evidence:

Hair Evidence:

• Hairs usefulness when solving a crime is very limited (poor discriminatory power)

• Not possible to determine if hair originated from a particular person based on physical appearance or morphology

• When hair obtained from root = valuable evidence

Sample required for hair analysis:

• Items searched for hair including clothing, balaclavas and motorcycle helmet

• Reference samples need to be taken

• Only a medical examiner should take reference samples of pubic hair

Morphology of hair layers

1. Cuticle - The outer layer covering the hair. Resistant to chemical decomposition and retains its structural features over a long period of time. Made of scales that point to the tip of the hair. Variety of scale patterns can be seen by scanning electron microscopy (SEM)

2. Cortex - Layer of cells within the cuticle. Contains the pigment granules (give hair color). Examined microscopically in a liquid medium to allow light to penetrate hair

3. Medulla - Collection of cells that look like a central canal running through hair. For animals diameter more than ½ hair, in humans its less than 1/3. In human hair medulla fragment is absent

Hair root:

Shape and size determined by growth phase of hair

→Follicular tag - translucent piece of tissue surrounding the hair’s shaft near the root

1. Anagen phase - Initial growth phase, when follicle produces hair root. Can last up to 6 years, when hair is pulled from the root some hairs in anagen phase have a follicular tag (DNA can be extracted)

2. Catagen phase - Hair growth rate decreasing. 2-3 weeks root bulb shrinks as it is being pushed out of follicle

3. Telogen phase - Hair growth has ended and root takes on club shaped appearance. 2-6 months hair pushed out of follicle and sheds

DNA analysis:

• Natural shedding - Hair in telogen phase, poor for DNA typing

• Forcibly pulled - Hair collected from some scenes often yield a DNA profile

• Mitochondrial - hair shaft can also be used where genomic DNA is limited

• Approx. 50 full length hairs from head is needed for a sample

Blood - Serology:

Serology - Scientific study of blood serum and other bodily fluids

→ Diagnostic identification of antibodies in the serum

Blood components: red blood cells, white cells, platelets and plasma

→ If blood is allowed to clot then liquid fraction is called serum

Blood groups / types:

• Before DNA typing, blood grouping was used with other serotyping methods to partially individualize a blood sample based on non-DNA genetic markers

• Pre DNA systems referred to as classical/ conventional genetic markers

Red blood cells- Carry oxygen around body but also have structures on cell surface known as antigen

→ Antigens are proteins made from the DNA inherited from our parents (30 grouping systems)

-A-B-O system and Rhesus (Rh) systems are the most importnt

ABO blood typing:

• Type A has A antigens on cell surface

• Type B has B antigens on cell surface

• Type AB have both A and B antigens

• Type O have neither

If a serum containing anti-B is added to RBC that have B antigen then antibody binds to antigen on cell surface

Agglutination - Each AB can attach to different RBC so a network of cross-linked cells is created

• The most common blood group world wide is O (46%)

• 80% of UK/Irish population are rhesus positive

• Your positive or negative status is added to your blood group

Other biological Fluids:

Semen:

• Important in SA cases

• presumptive and confirmatory tests available

• important source of DNA identification

-Acid phosphatase (AP) is an enzyme present in high quantities in semen and is quite stable.

Testing Methods:

→Turns purple in the presence of acidic solution and Fast Blue B dye. Moistened filter paper pressed on item and test solution added.

→ MUP (Methyl umbelliferyl phosphate) uses fluoresces under UV when it comes in contact with AP

→ PSA used in precipitation test where semen extract and AP form visible precipitation line between

• Spermatozoa - Sperm cells, unique to semen identification. Microscopic presence of semen confirmed

• Oldest confirmatory test presence

• Stained material is immersed in small amount of water, rapid stirring of liquid transfers some sperm to water

• Drop placed onto slide and observed under microscope

Persistence of semen:

• Spermatozoa should be found in the vagina 24 hours after, sometimes 48 hours and some cases up to 4 days later

• Shorter persistence for semen deposited in the anal intercourse

• Spermatozoa can survive 24 hours orally

• Can survive in deceased bodies, for longer in cool temperatures

• Can last indefinitely on clothing which has not been washed and kept in dry environment

Semen as DNA source:

• In order to perform DNA typing on sperm, it needs to be separate the sperm DNA from any other DNA

• Differential extraction - Performed involving the lysis of the non - sperm cells followed by centrifugation to remove the still intact sperm

Saliva:

• Useful source of DNA in criminal investigations

• DNA present in epithelial cells that transfer from the lining of the mouth cavity to the liquid

• Saliva can be transferred by spitting, mouth coming into direct contact with objects, Sexual intercourse

Phadebas Amylase Test:

• Detects the presence of alpha - amylase, if present a blue dye is released into solution.

• Amylase can be measured alternatively, with a spectrophometer or visualized on reagent-coated paper

Vomit:

• No specific test to identify

• Characteristics such as odor, appearance of sample

• DNA profiling usually successful on both bulk vomit and dry stains

Urine:

• Useful during investigation and often not visible

• Tests relatively insensitive due to dilution of its constituent characteristics urea and creatinine

• Unlikely to yield DNA because low presence of cells in fluid

• Small chance of getting DNA when concentrate enough cells from a large area of volume

Feces:

• Test can be carried out to indicate presence of urobilinogen

• DNA profiling usually unsuccessful

• Swab of surface of the formed stool is required before attempting DNA analysis