Forensics Methods of Identification
What is Forensic Science? • Forensic science is the application of scientific techniques to investigate a crime. • Forensic scientists collect and analyze evidence from a crime scene. • Police use this evidence to find out what happened and who was responsible. • The evidence can also be used in the legal system to convict someone of a crime. • What kind of questions can Forensic Science help us Answer? (Student Brainstorm).
Forensic Scientists • Forensic scientists will help to collect scientific evidence at a crime scene. • They can be specialists in a variety of fields: • Psychology • Dentistry • Anthropology • Medicine • IT • However regular police can also collect evidence at a crime scene if they have been specially trained.
Forensic methods of identification • It can often be difficult to determine the remains of a dead person, especially if all that remains are bones • However without proper identification it can be difficult to determine the identity of the living as well. • In the past criminals could just change their name and move to a new location. • What are some forms of identification we use today? (Quick Student Discussion) • Today we have various methods for identifying remains and establishing the identity of perpetrators
The Bertillon system • In 1870 the Chief of Criminal identification in Paris, Alpharose Bertillion designed a method for an identification system. • His system involved measuring and recording the dimensions of bony body parts • This was called anthropometry • The assumption was that no two peoples measurements were exactly the same • Disadvantage: This method eventually was retired in 1905 because a man was wrongly convicted and sent to jail for a crime his twin brother committed!
Photographic Identification • In 1854 photography was invented • In the 1870’s it was generally used with anthropometry for identification • By the 1900’s it was widely used by itself as a form of identification • Still widely used on various forms of identification e.g. Drivers licenses • Disadvantage: • Has limitations if used as the sole means of identification • Positive identification by a witness looking at an album of photos is difficult. Tony Mokbel
Identikit and Composite Drawings • Before photographs drawings of wanted criminals were commonly used e.g. Wanted Posters • Another System called Identikit gained popularity in 1960’s because it uses pre-drawn facial features that can be slotted together without the need of an artist. • More recently computerized methods can be used to create a drawing of a suspect in minutes. • Disadvantage: • It is often difficult for a witness to get all features correct • Only 2% of composition drawings ever led to a positive identification
Activity : Identikit Challenge • The Program will flash a face up for 10 seconds • You then have to reconstruct that face by selecting individual features • http://asistm.duit.uwa.edu.au/forensics/faces/
Biometric Facial Recognition • Specialized computer systems and software can quickly and accurately identity a person from a single stored image in a database. • Facial recognition measures the points between different facial features (eg Eyes, nose, ears and chin) and compares this to the files on a database
Fingerprints • Fingerprints are found on the palms of hands and soles of feet of all primates • They allow us to grip things • Each fingerprint consists of ridges and valleys • These will grow back in the exact some pattern
Fingerprinting Cont. • Fingerprints are compared in the following manner: • The same minutiae are present • The minutiae flow in the same direction • The minutiae occupy the same relative positions to each other
Activity: Super Prints! • Make a small bowl from the aluminum foil and place into a container • Place a small cup of hot water in the container • Press you finger onto a microscope slide • Add 10 to 15 drops of superglue into the bowl • Place the slide into the container and seal lid • Focus a light or heat lamp on the container • Once the finger print has formed see if you can identify some of the minutiae that are present
Project: Design your own crime science • The major piece of assessment for this unit will be a self designed crime. • In your self designed crime you must include a number of different pieces of forensic evidence that will conclusive indicate a specific suspect. These may be things like: • Finger prints • DNA tests • Handwriting analysis • Video surveillance • We will cover a number of these topics and more over the course of this subject • At the end of each week you must hand in the work you have done on the project: • In the first week this may be general brainstorming or the formation of a story narrative for your crime. • I will provide you with feedback on what you have submitted • The final three lessons of this unit will be as follows: • Finalization of project work (Single lesson) • Presentation and assessment of work by peers (Double lesson)
Additional Resources • List of forensic terminology: • http://suicideandmentalhealthassociationinternational.org/forensicsgloss2.html
Forensics From the eye to DNA
Iris and Retina Identification • A persons identity can also be identified using a biometric device, like a retina scanner. • These scanners will either examine the iris pattern or the blood vessels in the eye • These type of scanners are more accurate because: • Two scans are taken (one for each eye) • Cannot be forged with a glass eye • There are 266 identifiable features in the iris (this makes it far more accurate than a fingerprint) • Iris does not change over time
Forensic Odontology and anthropology • Odontology is the scientific study of teeth. • Odontology is often used by forensic scientists to identify a victim by his or her teeth • Forensic anthropology is the application of the science to study the remains of a human skeleton
Identifying a ‘known’ body • If there is sufficient evidence to assume the identity of a body (e.g. recovered from a house fire), x-rays of the body may be performed. • X-rays will show if any previous bone breaks have occurred or whether pins for serious breaks are present. • These are then compared to hospital records for the suspected victim • Additionally X-rays of the teeth are taken to compare to dental records as well
Identifying an “Unknown” body • It can sometimes be difficult to identify a corpse, especially if it is only a skeleton or individual bones. • However a forensic anthropologist can gather information about the body from careful examination of the bones. For example: • Femur (main bone of the leg) can be measured to determine the height of a person. • Whereas sex and age can be determined from examination of the pelvis and skull.
Activity: Inferring height form bone length Femur Humerus • In this activity you will measure various class members femurs • From this data we can try to infer the height of people in the class. • We will then check our results for accuracy! • Check handout for more information
DNA Profiling • DNA or Deoxyribonucleic acid is a very important molecule found in all living cells. • Its structure carries genetic information or a blueprint for an entire organism. • We get half of our DNA from both parents and as a consequence DNA is unique to an individual, except identical twins. • DNA fingerprinting or profiling was first used as technique in 1985 and was initially used to identify genetic diseases. It was used soon after in forensic science and criminal investigations
DNA – Deoxyribonucleic acid • The process begins with a blood or cell sample from which DNA is extracted. • The DNA is cut into fragments • The fragments are then separated by size via electrophoresis on an agarose gel. • The DNA band pattern can then be transferred to a nylon membrane or a photograph can be taken. • The band pattern formed is unique to every individual (except twins)
Activity: Who’s the father? • On left we can see two examples of DNA fingerprints one is simplified and the other complex. • On your handout are somewhat simplified DNA profiles for a child, its mother and two possible fathers. • Your job is to work out who is the father by comparing the DNA bands! • Remember bands present in the child have to come from either its mother or father.
Forensics Is it real?
Analysis of Handwriting • When we analysis handwriting we are trying to prove the identity of the writer. • This could be from a Ransom note or simply a signature on a check.
Activity: Handwritten forgery! • On a piece of paper sign your name twice. • Circle one of the signatures (this will be the reference sample) • Now swap the piece of paper and pen with a partner • Your partner will now attempt to copy your signature • Pass the piece of paper to a third person and see if they can spot which signature is the forgery!
Printer Matching • Print outs from a specific computer can be matched by how the printer leaves marks on the paper as the paper passes through the printer • This can be seen at low light and photographed. • Additionally the ink from the printer can also be matched.
Ink Analysis • Each brand of ink has its own “chemical signature”. • Slight variations in the chemical make-up of different brands of ink cause it to leave a different pattern when dissolved • Slight variations in the chemical make-up of different brands of ink cause it to leave a different pattern when dissolved
Activity: Ink Analysis • Draw a single dot or a line on a strip of chromatography paper. Approximately 4 cm from the bottom of the paper. • Fill a small beaker with ethanol so the liquid is only 1 to 2 cm high. • Place your strip of paper into the beaker so that only 1 to 2 cm is submerged and that your dot or line is only a few cm away from the ethanol.
Ink Analysis • Problems associated with the method used in class: • Destructive test (can’t do it if evidence must be preserved) • Difficult to differentiate between inks with a very similar signature with the naked eye. • “Crude” method of identification. • Other non-destructive methods of forensic ink analysis: • Infrared luminescence/reflectance (where infrared is used to identify chemical signatures. • Capillary electrophoresis (where a tiny amount (nanoliters) of the ink is injected into a silica capillary filled with a buffer solution, then an electrical current is passed through it. • Databases for these two methods are currently being compiled.
Forgery • Many criminals attempt to forge many types of currency or other documents • Therefore the government and banks have developed technologies to make it more difficult to make successful forgeries. • Upon closer examination of forged bills some common mistakes are: • Identical serial numbers • Poor printing paper • Differences in printer inks • Lack of UV markers
Forensics: Collecting Evidence
What is evidence? • Wherever you go and whatever you do you leave behind proof that you were there. • In a criminal investigation this is called evidence. • Evidence can come in various forms.
Can you think of different types of evidence you might find at a crime scene?
Types of evidence • Evidence could be: • Eyewitness – they can give written or verbal accounts. • Physical evidence: • Fingerprints • Shoe prints • Hair or fibers • Blood • Digital evidence
Collecting Fingerprints • A common for of evidence is the finger print. • Fingerprints are formed from contact with non-porous surfaces: • Glass • Plastic • Mirrors / Windows • Steering wheels • Light colored surfaces are ‘dusted’ with a black carbon powder, while white aluminum powder is used for dark surfaces.
Porous surface fingerprints • Fingerprints can be picked up on porous surfaces such as: • Stone • Raw or unpolished wood • Technique involves using high powered ‘Poly lights’ that cause fingerprints to fluoresce
Collecting Body Products and Fibres • Whether a fibre is synthetic or derived from an organism it can be examined under a comparison microscope. • However finding a match from one fibre at a crime scene and one from a suspect is strong circumstantial evidence but not conclusive
Collecting Impressions –Tool Marks • Most crimes are committed using a variety of tools such as: • Pistols and Knives • Crow Bars and Wire cutters • Screw Drivers and Hammers • When criminals use these tools to commit a crime they can leave behind marks or damage to material or persons they come into contact with.
Tool Marks • The marks made are generally lines (called Striations) are caused because of imperfections on the surface of the tool. • Tools used on human tissues do not generally leave marks or striations. • However wounds found on a victim can generally indicate, the size, shape and length of a weapon.
Track Impressions • Impressions can be left behind from our feet, shoes or even the tyres of our cars. • How might tracks be left behind? • Despite that shoes and tyres are mass produced to be identical there are still slight Imperfections that can tell individual tracks apart.
Activity: Tyre Prints • Paint a small section of each tyre with black paint • Place paper on the section that has been painted • Peel the paper off and wait for it to dry. • While it is drying collect other tyre samples • Now swap your images with another group. Can you match the impressions to particular tyres?