Powerpoint to help with unit 32 M6 D6: Biological techniques

1. Powerpoint to help with unit 32 M6 D6: Biological techniques

2. Blood group analysis

3. What is blood typing? • Blood typing is using serums containing antibodies to determine what antigens a person’s blood contains. This can then be used to deduce what blood type the person is.

4. What is blood? • Blood is a circulating tissue composed of fluid plasma and different cells. • Blood moves around the body in blood vessels and is circulated by the heart. • The most common type of blood cell is the red blood cell (RBC), or erythrocyte. • The role of the RBC is to deliver oxygen to body tissues via the haemoglobin protein molecules inside red cells. • Mammalian RBCs are flat circular shaped and depressed in the centre and they lack a nucleus

5. Human and animal red blood cells have antigens - extracellular glycoprotein structures, located within and sticking out from the RBC membrane. • These surface antigens give a specific blood-type characteristic to the cells, which determines a person’s blood group. • Variations in the antigens on RBC membranes creates different blood group types • Forensic blood typing analysis determines which antigens are present on the RBC surface and therefore identifies the blood group of an evidential blood sample

6. How blood typing in forensic works • If a blood type with a different antigen is injected into a person’s body (e.g. someone with only type A blood is injected with type B blood), then their immune system will produce antibodies to attack the type B blood • This means that there would be a chemical reaction between the antibodies produced from the immune system and the B antigens- which looks like dots or clumps called agglutinogens

7. Synthetic antibodies are used to determine what antigens are present in blood. • Antibody A will react with the A Antigens • Antibody B will react with the B Antigens • Antibody Rh will react with the Rh Antigens • An individual with only A antigens present on the surface of their RBCs is categorised as blood type A • Those who have only B antigens present are categorised as type B. • lf A and B are present the blood type is AB. • If neither antigen is present the blood type is group O.

8. Evaluating Blood typing • The identification of blood group cannot identify an individual, but can help eliminate those who possess other blood group types from the inquiry. • Overall is a cheap and simple technique. • The results collected from this technique are qualitative data hence different people may have different interpretations of the same result. • This technique is used when a violent crime has taken place and blood evidence has been collected.

9. Genetics analysis (DNA sequencing, genetic fingerprints)

10. What is DNA? • Deoxyribonucleic acid (DNA) is the genetic material that carries hereditary information from one generation to the next. • DNA is a large molecule tightly packaged into chromosomes in the nucleus of a human cell. • DNA provides the genetic information for each individual and determines their physical characteristics, e.g. eye colour, hair type and height. • Every cell containing DNA within an individual has the same genetic information and every individual's DNA is unique (apart from identical twins who originate from the same fertilised egg). • Therefore DNA can be used to identify individuals.

11. Genes are a small section of DNA and are made up of a sequence of nucleotide bases that determine the amino acid sequence. • Different sequences of amino acids code for different proteins in the human body. These protein coding regions, or exons, are very similar in different individuals. • There are also non-coding regions that do not have any genetic function and mutations can occur in these regions that do not affect protein production. • The non-coding regions and are responsible for the small amount of differences between two individuals‘ DNA sequences. • These differences are termed 'polymorphism' and are the key to genetic analysis.

12. How genetic analysis works in Forensics • DNA sequencing involves determining the exact sequence of nucleotides in a fragment of DNA. • This can be useful when determining what species a DNA sample belongs to • DNA fingerprinting does not concern the exact sequence of nucleotides. It involves comparing fragments of different DNA samples • The goal of fingerprinting is to determine if a sample of DNA containing material comes from an individual OR to carry out paternity/maternity testing

13. DNA fingerprinting is cheaper and faster than DNA sequencing but gives you less information • DNA fingerprinting is used in forensics while DNA sequencing is used in scientific research where scientists need to know the sequence of a piece of DNA • The Restriction fragment length polymorphism (RFLP) technique was developed in 1984 and is the main method used to produce DNA fingerprints/DNA sequences that can be analysed. • The main stages of RFLP are shown on the next slide

15. How RFLP works • RFLP involves the use of restriction enzymes that digest and cut the extracted DNA to produce fragments of repeating DNA sequence. The small DNA fragments can then be separated using gel electrophoresis and their size analysed • The most common DNA samples analysed in the forensic laboratory are blood, semen, epithelial skin cells and muscle tissue. These all contain DNA except for red blood cells which do not have a nucleus; however, white blood cells do contain DNA and can be genetically analysed.

16. Stage 1 of RFLP: DNA Extraction • To extract DNA, the cell membranes, structural materials, and proteins and enzymes are destroyed by an alkaline solution at high temperature (50-'100'C) so the DNA can be released and safely separated from the rest of the cell components.

17. Stage 2 of RFLP: DNA Digestion • DNA-cutting restriction enzymes are added to the extracted DNA which digest the DNA into hundreds of small fragments. • The enzymes are extremely specific and only cut across the DNA molecule in certain locations when they recognise a particular sequence of nucleotides, called a restriction site

18. Stage 3 of RFLP: DNA Separation • Once the DNA has been digested into many small fragments, the DNA pieces must be separated so they can be analysed. • This is done using gel electrophoresis, a technique that separates large molecules, across a plate made of gel, on the basis of the size and electric charge of the molecule. When separating the DNA fragments, the smaller and lighter fragments will move further down the gel plate than the larger and heavier fragments

19. The difference in rate of movement causes the different sized pieces of DNA to move different distances and therefore separate on the gel. • DNA fragments of the same size move to the same position on the gel and form a pattern of DNA bands.

20. Stage 4 of RFLP: DNA Visualisation • It is not possible to see the DNA fragments on the electrophoresis gel and an enhancement technique must therefore be used to visualise the DNA band pattern. • Firstly, the Southern blotting technique is used, where a nitrocellulose membrane is laid on top of the gel and the DNA bands transfer to its surface. • Secondly, the membrane is then soaked in a solution containing radioactively labelled pieces of DNA, called probes, which recognise and bind to specific sequences of DNA on the membrane, a process known as hybridisation.

21. Finally, The excess probe is washed away and the membrane is exposed to an X-ray film, a method called autoradiography. • The radioactively labelled DNA fragments leave an image on the film that, when developed, shows the location of each band of DNA fragments; this pattern is known as the DNA fingerprint

22. Stage 5 of RFLP: DNA Analysis • To measure the DNA fragments, a standard marker is run alongside the DNA samples on the electrophoresis gel, which appears next to the DNA fingerprint on the film. This marker is called a DNA ladder and is composed of a number of pieces of DNA of known length. • By comparing the distances the unknown pieces of DNA move in relation to the DNA ladder fragments of known size, it is possible to establish the size of the unknown fragments.

23. Usually in the forensic laboratory, unknown crime scene DNA samples are separated next to suspect reference DNA samples, which allows direct comparison of the DNA patterns. • lf the two DNA fingerprints have the exact same DNA band pattern with DNA fragments of the same size, then the suspect is the source of the crime scene DNA sample. lf the pattern does not match exactly, then the DNA did not originate from the suspect.

24. Evaluating genetic analysis • It is used when a material containing DNA is found at a crime scene, where the DNA will be analysed to establish if it matches the DNA of a suspect • It can also be used in maternity/paternity testing • It can also be used to confirm if the DNA sample comes from a human or a different animal. • Overall this method is relatively expensive • It cannot be used to differentiate between identical twins as they have the same DNA • It can be used to eliminate suspects, and with the exception of identical twins/siblings, each individual has their own unique DNA sequence

25. fingerprint identification and analysis

26. What are fingerprints? • Fingerprints are the most common type of evidence found at crime scenes and are associated with a wide range of crimes. • Fingerprints are biological characteristics that are unique to every individual and are formed during fetal development

27. How fingerprint identification/analysis in Forensics works • Fingerprinting is a system of identification based on skin ridge patterns on fingertips. Friction skin ridges are a series of elevated lines of skin of different sizes and formations called ridges (or hills), the long deep grooves in between are called furrows (or valleys). • Friction ridge skin is present on the surface of palms, palm side of fingers and thumbs, and soles of feet and is designed by nature to provide us with a firm grip and to resist slippage.

28. Once the type of fingerprint has been determined (whorl, loop, arch and composite) the ridges are analysed as follows: • Ridge counting: This is counting the number of ridges between the core of the fingerprint and the delta of the fingerprint • Where the ridges are: This involves locating exact positions of the ridges delta

30. Fingerprint ridges have a number of different types of characteristic, or minutiae, that can be used to identify and compare fingerprints • Until recently, a forensic scientist had to find 16 matching minutiae in two fingerprints to identify them as from the same source. this led to many fingerprints being declared as not matching even when the fingerprint examiner was convinced it was a match. • Today, there is no minimum number of minutiae necessary to identify a match, and the decision is left to the discretion of the trained and experienced forensic scientist.

31. Evaluating fingerprinting • Fingerprints have a high evidential value as they can uniquely associate a person with a crime scene or evidentiary item. Even identical twins will have different fingerprints. • Fingerprints are one of the last features to be lost from the skin during decomposition and in certain circumstances can be used to identify dead bodies months or even years after death.

32. Some criminals have made attempts to “remove” their fingerprints (e.g. by dipping their finger tips in strong acid) BUT when the fingers heal the fingerprints remain unchanged. • When a fingerprint is found at a crime scene, it is sent to the forensic laboratory for analysis where it is scanned into the Fingerprint Database. This database contains records of fingerprints from convicted criminals and suspects that were not convicted. There are concerns about the storage of innocent individuals’ fingerprints that were only classed as suspects and were not convicted.

33. It is appropriate to analyse fingerprinting as it is the most common evidence found at a crime scene. It can be used to determine the identify of a fingerprint found at a crime if it is successfully matched to a fingerprint of a known suspect.

34. bone and skeleton physiology analysis

35. What is Forensic anthropology? • Forensic anthropology is the study of bones or human remains • Bones often survive the process of decay by many years and provide an important form of identification after death. • A forensic anthropologist is a bone specialist who applies standard scientific techniques developed in physical anthropology to identify decomposed, mummified, burned or dismembered human remains. • They examine skeletons to identify victims; by establishing the biological profile of the skeleton, they can identify: gender, age at death, heightand racial ancestry.

36. How does forensic anthropology work in Forensics? • Forensic anthropologists will measure the size of the bones and use this to make estimate the size of missing bones as well as confirming characteristics about the person’s remains • They will also look for unusual marks, fractures and holes which could indicate how the person died, if they were attacked or a victim of abuse and torture

37. Forensic anthropology: Determination of gender • skeletons of males are generally larger in size and more robust than females. • The skulls of males usually have a wider jaw, squarer chin, more sloping forehead and more pronounced eyebrow bones than females. • Differences in shape can be seen in the male and female pelvis, as the female pelvis is designed to be able to give birth.

38. Forensic anthropology: Determination of stature • The most common method for estimating living stature (height and build) from a skeleton is to measure the lengths of the long limb bones, as long bone length is proportional to height. • Ideally, the forensic anthropologist will have the six upper and six lower long bones; however, height can still be determined when the remains of only one long limb bone are present. • Precise measurements are obtained using an osteometricboard and the measurements are input into mathematical formulas developed through gender research to produce a fairly accurate estimate of stature, with a small standard of error.

39. Forensic anthropology: Determination of age • As individuals age their bones grow, change and eventually deteriorate, and the typical changes that occur over time can be used to determine the age of a victim when they died from their skeletal remains. • The techniques used to age child and adult skeletons are different as the bones of children are still growing, and methods for determining age of children at death are therefore based on the growing skeleton and changes to the teeth.

40. In contrast, adult bones are fully grown and weaken with time, and when examining adult skeletal remains the changes related to deterioration are used to estimate age. • In addition to bone growth, the teeth of children are also growing and changing as they get older and these dentition changes can be used to age child skeletons. • Teeth contain enamel, one of the hardest substances in the human body, which makes teeth very strong and resistant to degradation. ln fact, they are the last part of the body to decompose, and can withstand extremely high temperatures in a fire, so they are often a useful source of identification in murder or mass disaster investigations. (This is done by comparing teeth remains to dental records).

41. Evaluating bone and skeleton physiology analysis • This is appropriate to be used when searching, locating, excavating and recovering suspicious buried or surface remains at the scene of a crime, and are often called to scenes of mass disasters and war graves to identify bone fragments and teeth and identify victims • In many murders, suicide, accidental and mass disaster cases, when a body is recovered a while after death has occurred, the tissues of the body have decomposed so traditional means of identification, for example visual identification of the victim or a forensic post mortem of the body, are not possible

42. Evaluating bone and skeleton physiology analysis • A lot of information can be obtained from this technique • Sometimes mitochondrial DNA is present which can be analysed • The information generated is often based on assumptions

43. hair and fibre identification and analysis

44. What is hair and fibre identification and analysis? • Head hairs are shed by individuals each day onto clothing and items in our environment, and this makes hair a very common form of forensic evidence. • In addition, loose animal fibres can easily be shed from the clothes that we wear into our environments. • Both of these types of evidence may be transferred during physical contact between a suspect and victim or crime scene, and can be used to reconstruct the events of a crime. • Animal hairs are natural fibres and these are also analysed in the forensic laboratory for criminal cases such as theft of animals and furs, or illegal breeding, and may be an additional source of linking evidence in any human case where the victim or suspect has a pet

45. Hairs can be transferred directly from the region of the body where they are growing. This is called primary transfer and occurs when hairs fall from the head onto an item of clothing, seat cover or floor. • In secondary transfer hairs do not transfer directly from the area of growth, but from a location where hair has already fallen. For example, from an item of clothing onto the floor or from a seat cover onto an item of clothing. This means that a suspect could carry on their clothes a hair from an innocent person (primary transfer) and transfer it to the crime scene (secondary transfer), making the innocent person look guilty.

46. Structure of hair • Each hair fibre consists of three main microscopic structures: • the cuticle, a hard outer layer that protects the hair shaft • the cortex, surrounding the medulla, which is the main bulk of the hair • the soft medulla at the centre of the hair.

47. Structure of hair

48. When analysing hair, the Forensic examiner will try to answer the following questions: • What is the cuticle pattern? • What is the degree of medullation and medullary index? • What colour is the hair? What is the size, distribution and concentration of pigment granules? • Is a root present? • Did hair fall out or was it pulled? • What is the condition of the hair and tip? How was the hair cut, treated or damaged? • Is the hair human or animal? • If human, child/adult? Male/female? Which racial group? What part of the body is the hair from? • lf animal, which species? • Does questioned hair recovered from scene compare to reference hair from known individual?

49. How does hair/fibre analysis work in forensics? • The forensic analysis of hair evidence usually involves the use of comparison microscopy, where the structure and characteristic features (e.g colour, cuticle) of questioned hairs are compared to known hair samples. • The comparison microscope is a specialised forensic microscope usually used to analyse hair evidence and other types of trace evidence. The comparison microscope consists of two connected compound light microscopes that allow two samples of hair; or other microscopic types of forensic evidence, to be viewed next to each other at the same time

50. For example, in a comparison microscope, a glass microscope slide holding questioned hairs from a sexual assault crime scene is positioned on the stage of one microscope, and a slide with known reference hairs from a suspect is positioned on the stage of the other microscope. • The microscopic characteristics of the two samples can be examined and compared directly in one field of view, allowing feature differences and similarities between the known and questioned hairs to be easily observed