Serology

Study of bodily fluids Major component of crime scene processing and analysis Serology tests are fast, efficient and inexpensive Applies to blood, semen, vaginal secretions, saliva, sweat, tears, vomit and urine prior to further analysis Identifies proteins associated with specific body fluids, but are biologically generic The proteins used to detect semen in one body are the same proteins that exist in any other semen stain.

Serology Violent crimes most likely to produce body fluid evidence. Bodily fluids can be found in an infinite number of places Saliva can be found on cigarette butt, licked stamp or drinking glass Sweat, tears and semen can be found on clothing and bed sheets. Skin and other tissues left on a vehicle after a hit and run accident. Any fluids can be found on the skin or transferred to the perpetrator or victim

Questions for Investigator at crime scene What type of body fluids might be present? What state is that fluid in – liquid or dried, fresh or degraded? Is the fluid from a human or animal? Factors impact on collected and identified Liquid blood has more genetic markers in it than dried blood and can be taken up with a syringe. Dried blood resists bacterial growth better and is more stable. Could blood be from dog that tried to defend the victim

Serology Science of Serology can be used to answer all those questions and some can be answered at the crime scene. It can even exclude a person as a suspect just like we saw with hairs Serology can not tie body fluid to a specific and unique source. DNA testing is need for that

Presumptive vs. Confirmatory Presumptive Test A quick and dirty way to figure out the likelihood of whether something is what you think it is in the field. Helps investigators determine where blood and other bodily fluids may be at a crime scene. That will help them determine what happened and what evidence to collect. Can give a false positive result but that can be sorted out at the lab later. Never want to use a field test that can produce a false negative result or investigators would walk away from real crime scene thinking there job was done. Must be followed up in a forensic lab with a confirmatory test

Presumptive vs. Confirmatory Highly sensitive to but not specific for a particular substance Color test indicating that a stain is blood but not what kind of blood (human vs. nonhuman) False positives are acceptable (may not be blood but something reacts with the chemicals used in the test) False positives are acceptable as long as no false negative results are obtained Positive results can be more specifically tested for the second type of test. Confirmatory Test More reliable and discrimnatory but more costly and timely

Presumptive Test Luminol is the method of choice where perpetrator has tried to clean up the crime scene Detects blood in a minute quantities ( 1 part blood per 10 million of something else)

Luminol Perpetrator cut up a woman in his basement and thought he had washed the blood down the drain and painted the concrete floor. The little bit of blood mixed with the paint that he couldn’t see himself was still there and detectable with luminol

Pros and cons of Luminol What is the limitation with luminol? It doesn’t work if chlorine bleach is used to clean up blood. Pros Can be used in the field Dilutes a sample, complicates but does not completely ruin the blood for further testing.

fluorescein Precursor to luminol that goes back to the early 1900s Still used today because it does not react with chlorine bleach It is a thicker chemical and sometimes easier to use on a vertical surface due to gravity

What you see on TV Not luminol Fluorescein being used in UV or blue light with orange goggles.(dramatic) Luminol does not need lights. It needs darkness. Both are good for finding stains that someone has tried to clean up after a crime. White marks are seen when someone has tried to clean up not a blood spatter pattern (CSI shown clean wall being sprayed with chemicals but when lights turned out, we see a bunch of spots not a cleaning smear)

Other Presumptive Blood Tests Moist cotton swab with a dab of suspected blood on it and place it on a test strip –Turns blue green then sample is blood Leucomalachite green – turns green if blood present Kastle-Meyer Test – most commonly used field test Uses phenolphthalein and hydrogen peroxide to detect hemoglobin in rbc Turns a dark pink color Hemoglobin Ancient oxygen carrying protein Found in animals with a backbone

Human blood typing Karl Landsteiner figured out how to type blood in 1901 Won Nobel prize in Medicine for discovery in 1930 In 1925, it was discovered that about 80% of population are secretors. Secretors secret a variety of proteins native to their blood in sweat, saliva, tears, urine etc. making it possible to determine a person’s blood type using non blood secretions.

Human Blood Typing Two Systems: ABO system Rh Protein ABO system Cell membranes have proteins on the surface called antigens Antigens come in two forms: A and B

Immunology Study of interaction between antigens and antibodies Antigen Anything the body reacts to by producing an antibody Antibodies Proteins our immune system makes to fight off a specific intruder

Immunology Antibodies are develop by vaccines and exposure to illnesses In ABO blood system, we are each born with genetically determined antibodies in liquid part of our blood known as plasma Have antibodies to the opposing red blood cells that we might encounter in each other Ex. Type A blood has A antigens but B antibodies

Immunology Antibodies attack and attach to foreign antigens in order to deactivate them. Reaction between antibodies and antigens is called agglutination (clumping) Antibody antigen complex precipitates out of the blood and then is destroyed by white blood cells

Immunology Scientist have capitalized on the formation of these complexes and developed test to determine blood type based on the concept. Treat the blood with antibodies and see what those antibodies cling to and pick up. Piece of evidence containing blood (shirt) Use commercially prepared solution of antibodies. Some antibodies will attach and other will not. Washing step gets rid of antibodies that do not attach Elution: heat up sample high enough to break antigen/antibody bonds Antibodies that did match to the blood sample can be removed and tested Anti A = A typeAnti B = B typeAnti A and B = AB type

Blood found at a crime scene Congealed puddle (clots in about 5 minutes) Blood arrives in the lab on a variety of surfaces Crime labs deal with blood and other fluids that are contaminated and old Have commercially stock solutions of antibodies that identify the antigens in humans and types of animals.

Paternity Testing Used blood typing before DNA technology A form and B form are codominate Type A and type B are codominate genes Type O is recessive Can a mother who is blood type B and a father who is blood type A ever have a child who is type O?

Charlie Chaplin and Joan Barry Joan Barry accused Chaplin of being the father of her child Chaplin was reportedly type O Barry was reportedly type A and her child was type B Could Charlie Chaplin have fathered Barry’s child? No, but Chaplin had to pay child support anyway because blood test were not admissible in court in those days. Case prompted California to reevaluate allowing blood testing to be admissible in court.

Blood Type Class evidence

Presumptive Test for other bodily fluids Acid phosphatase Chemical produced in male reproductive glands in seminal vesicles Glands produce bulk of the fluid part of semen Acid phosphatase is fairly common in nature (female secretions, plants fungi etc) If Acid phosphatase is found at a crime scene, it is considered presumptive evidence for semen False positives are allowed but not false negatives with regards to field tests

Confirmatory test for bodily fluids Microscopic exam to look for semen (even if dead or degrading) What about if male had a vasectomy? PSA (Prostate-specific antigen) is a confirmatory test for semen