Biological Forensics

Forensics Lab Objectives Learn the definition of forensic science. Examine ways biological information can be used to solve crimes, and see examples of this in today’s society.

Forensic Science Definition: The application of the tools of science, as well as specific scientific facts, to help solve legal problems Goal: the determination of the cause, location, and time of death

Some Uses of Forensics Identify potential suspects whose DNA may match evidence left at crime scenes Exonerate persons wrongly accused of crimes Identify crime and catastrophe victims Establish timing and circumstances of a crime http://www.rit.edu/~vjrnts/forensics/labs/lab1/lab1pix.html

Categories of Forensics DNA Evidence Forensic Entomology Forensic Serology Forensic Odontology Forensic Entomology Study of insects to estimate the time of death Insects lay eggs that hatch into larvae Stages of development tell how long ago the eggs were laid Temperature and other weather conditions affect the development Serology: looking at blood serum, also 80 -85% of the population are secretors: saliva, semen, vaginal fluid Historical methods of identifying and individualizing blood and other body fluids Antigen-Antibody reactions Enzyme-Substrate reactions Odontology looks at dental records in order to identify victim, also bitemarks on victim or objects at crime scene Bluebottle blow fly

Radiocarbon dating of the Dead Sea Scrolls Forensic Fingerprinting Fingerprint counting number of typica Forensic Anthropology Radiocarbon dating of the Dead Sea Scrolls As each atom decays, it changes from carbon to nitrogen and in the process emits a particle called an electron – this is radioactivity. These radioactive emissions can be measured to find out how much radiocarbon has decayed and how much still remains. C14 has a half-life of 5,730 years, which means that the level of radioactivity will fall by half its original amount over that period. So from the proportion of C14 to C12 in the organism, scientists can work out reliably how long ago it died. Forensic Antrhopology: Identification and examination of skeletal remains Bones can reveal species, sex, approximate age, race and skeletal injury Facial reconstruction can help identify “John or Jane Doe” Forensic Art Composite art, image modification, age progression, post-mortem reconstruction and demonstrative evidence

Bloodstain Pattern Analysis Forensic Photography Forensic Pathology Forensic Psychiatry Forensic Toxicology Bloodstain Pattern Analysis Forensic Photography Forensic Pathology Investigation of sudden, unnatural, unexplained or violent deaths Autopsy performed to establish the cause of death Manner of death classified as natural, homicide, suicide, accident or undetermined Time of death determined by rigor mortis, livor mortis and algor mortis Forensic pathology: coroner, 50% of deaths observed are by natural causes Forensic Psychiatry Study of human behavior Determine if persons are competent to stand trial Develop a suspect’s behavioral profile based on previous patterns of other criminals Psychology: often testifies in a court, for example, if they feel a person may be competent to stand on trial, Toxocology: tests different toxins in body, ie. Death due to poisoning, or perhaps accidental death due to bee sting Bloodstain pattern analysis gives an idea of what actually occurred at time of death, experts are careful of bugs and cockroaches that spread blood around

Biological Forensics Use of Entomology Use of Molecular biology (the study of insects) Use of Molecular biology (DNA analysis)

Molecular Forensics Use of identifying characteristics of molecules in our cells to aid legal investigations Compare the DNA and/or blood type of crime scene evidence to that of suspects, or use this information to identify a victim.

Two main methods of Molecular Forensics PCR (Polymerase Chain Reaction) Blood typing

PCR (Polymerase Chain Reaction) Developed in 1987 Amplify one molecule of DNA into billions of copies in a few hours Identifies an individual based on microscopic amount of evidence 99% accuracy rate Only one-tenth of a single percent of DNA (about 3 million bases) differs from one person to the next. Scientists can use these variable regions to generate a DNA profile of an individual, using samples from blood, bone, hair, and other body tissues and products. In criminal cases, this generally involves obtaining samples from crime-scene evidence and a suspect, extracting the DNA, and analyzing it for the presence of a set of specific DNA regions (markers). Scientists find the markers in a DNA sample by designing small pieces of DNA (probes) that will each seek out and bind to a complementary DNA sequence in the sample. A series of probes bound to a DNA sample creates a distinctive pattern for an individual. Forensic scientists compare these DNA profiles to determine whether the suspect's sample matches the evidence sample. A marker by itself usually is not unique to an individual; if, however, two DNA samples are alike at four or five regions, odds are great that the samples are from the same person. If the sample profiles don't match, the person did not contribute the DNA at the crime scene. If the patterns match, the suspect may have contributed the evidence sample. While there is a chance that someone else has the same DNA profile for a particular probe set, the odds are exceedingly slim. The question is, How small do the odds have to be when conviction of the guilty or acquittal of the innocent lies in the balance? Many judges consider this a matter for a jury to take into consideration along with other evidence in the case. Experts point out that using DNA forensic technology is far superior to eyewitness accounts, where the odds for correct identification are about 50:50. The more probes used in DNA analysis, the greater the odds for a unique pattern and against a coincidental match, but each additional probe adds greatly to the time and expense of testing. Four to six probes are recommended. Testing with several more probes will become routine, observed John Hicks (Alabama State Department of Forensic Services). He predicted that DNA chip technology (in which thousands of short DNA sequences are embedded in a tiny chip) will enable much more rapid, inexpensive analyses using many more probes and raising the odds against coincidental matches. PCR Analysis Polymerase chain reaction (PCR) is used to make millions of exact copies of DNA from a biological sample. DNA amplification with PCR allows DNA analysis on biological samples as small as a few skin cells. With RFLP, DNA samples would have to be about the size of a quarter. The ability of PCR to amplify such tiny quantities of DNA enables even highly degraded samples to be analyzed. Great care, however, must be taken to prevent contamination with other biological materials during the identifying, collecting, and preserving of a sample.

Some Interesting Uses of DNA Forensic Identification ID 9/11 victims ID plane crash victims ID Missing children DNA Shoah Project Tomb of the Unknowns Son of Louis XVI and Marie Antoinette Nicholas Romanov Peruvian Ice Maiden African Lemba Tribesman Super Bowl XXXIV Footballs and 2000 Summer Olympic Souvenirs Study migration patterns Poached animals DNA banks for endangered species http://www.ornl.gov/sci/techresources/Human_Genome/elsi/forensics.shtml

Forensic Serology Antigen-Antibody reactions Serum:The liquid that separates from the blood when a clot is formed. Blood clots when fibrin (a protein) traps and enmeshes the red blood cells.

Forensic Serology Antibodies secreted from b-lymphocytes Serum:The liquid that separates from the blood when a clot is formed. Blood clots when fibrin (a protein) traps and enmeshes the red blood cells.

Blood Artery White blood cells Platelets Red blood cells

Blood Plasma-55% Buffy coat-<1% Formed elements-45%

ANTIGENS

ANTIGENS b a b a b b a a b a b a b b a a

AGGLUTINATION

Blood being tested Serum Anti-A Anti-B Type AB (contains agglutinogens A and B; agglutinates with both sera) RBCs Type A (contains agglutinogen A; agglutinates with anti-A) Type B (contains agglutinogen B; agglutinates with anti-B) Type O (contains no agglutinogens; does not agglutinate with either serum) Figure 17.16

Can this blood be associated to a particular individual? MAYBE!?! Assume that type O blood is found at the crime scene. Type O occurs in about 45% of Americans. If investigators type only for ABO, finding that the "suspect" in a crime is type O really doesn't reveal very much. If, in addition to being type O, the suspect is a blond, and blond hair is found at the crime scene, you now have two bits of evidence to suggest who really did it. However, there are a lot of Type O blonds out there. If you find that the crime scene has footprints from a pair of Nike Air Jordans (with a distinctive tread design) and the suspect, in addition to being type O and blond, is also wearing Air Jordans with the same tread design, you are much closer to linking the suspect with the crime scene. In this way, by accumulating bits of linking evidence in a chain, where each bit by itself isn't very strong but the set of all of them together is very strong, you can argue that your suspect really is the right person.

Blood Type & Rh How Many Have It Frequency O Rh Positive 1 person in 3 37.4% Rh Negative 1 person in 15 6.6% A 35.7% 1 person in 16 6.3% B 1 person in 12 8.5% 1 person in 67 1.5% AB 1 person in 29 3.4% 1 person in 167 .6%

In Class Assignment Analyze 4 suspects blood types Compare it to blood found on the murder weapon. Determine the murderer.